The Netherlands, Italy, Germany, Belgium and Switzerland have already qualified after winning their groups but four more automatic places for first-place finishers are still to be decided.
There are also six more spots to be filled for next month's playoffs for the eight best second-place teams, with Sweden and Croatia already certain of being in the Oct. 21 draw.
Here are five things to know about Tuesday's qualifiers:
ONE POINT ENOUGH FOR SPAIN
Barring a major upset, Spain will be defending its world title next summer.
The Spanish, who are also the reigning European champions, need just a point from their home match against Georgia to secure top spot in Group I ahead of France.
France is three points behind in second place, so must beat Finland at home and hope Georgia can pull off one of the biggest upsets in recent qualifying history for Spain to be dumped into the playoffs.
"They will play very defensively. But the truth is that while we often have trouble in those types of games, very few times do they escape us," said Spain striker Alvaro Negredo, whose team needed an 86th-minute goal from Roberto Soldado to edge Georgia 1-0 in their first meeting.
The main problems for Spain coach Vicente del Bosque will be choosing a striker and goalkeeper. Del Bosque went with Michu up front to start Friday's 2-1 win over Belarus, but it was substitute Negredo who scored late for what proved to be the winner. Victor Valdes started that game as Spain's goalkeeper, leaving captain Iker Casillas on the bench.
The Spain game will be played in Albacete, near playmaker Andres Iniesta's home village.
A REPEAT OF 1973?
It was, and forever will be, one of the most painful episodes in the history of England's national team.
In 1973, England needed to beat Poland at Wembley Stadium in their final World Cup qualifier to advance to the following year's tournament in West Germany, but could only draw 1-1 after an extraordinary goalkeeping performance from Poland's Jan Tomaszewski.
The same scenario presents itself 40 years on.
With second-place Ukraine expected to run through San Marino in their last group game, the likelihood is that England — top of Group H by a point — will have to claim three points against the already-eliminated Poles to top the group and avoid the playoffs.
"I think they'll want to come here and win the game, get another good result, just like they did in '73, so we're going to be prepared for the very best Poland they can be," England coach Roy Hodgson said.
Poland has lost its last six away matches against England and hasn't won in 15 games against its opponent. So Ukraine probably isn't too hopeful.
A WORLD CUP WITHOUT CRISTIANO RONALDO?
The thought of Cristiano Ronaldo not being present at football's biggest tournament doesn't bear thinking about for some fans, but that prospect is likely to still be in the balance after the finale to Group F.
Russia leads the group by three points so if it wins or draws in Azerbaijan, second-place Portugal will be consigned to the playoffs whatever its result at home to Luxembourg.
"We have no feeling of euphoria because we have not qualified yet," Russia defender Dmitry Kombarov said.
After drawing at home to Northern Ireland and failing to beat Israel home or away, the Portuguese haven't done enough to go through as group winners, just like in qualifying for the 2010 World Cup and the 2012 European Championship when they needed to get past Bosnia both times in the playoffs to reach the finals.
Ronaldo isn't available for Portugal on Tuesday as his booking late in the 1-1 draw at home to Israel on Friday leaves him suspended. It does mean, however, that the Real Madrid forward would have a clean disciplinary slate going into next month's playoffs.
BOSNIA-HERZEGOVINA ON VERGE OF FIRST MAJOR FINALS
Since gaining independence in 1992, Bosnia-Herzegovina hasn't qualified for a major football tournament despite those near misses in the playoffs against Portugal.
That could all change on Tuesday.
Level on points with Greece in Group G but boasting a vastly superior goal difference, Bosnia-Herzegovina will seal its passage to Brazil by beating Lithuania away. With striker Edin Dzeko one of the in-form strikers in qualifying with 10 goals, it would be a major surprise if the team failed to finish off the job.
Bosnia-Herzegovina coach Safet Susic was part of the talented Yugoslavia side that made it through to the World Cup quarterfinals in 1990, where it lost to eventual runner-up Argentina on penalties.
BATTLE FOR SECOND
The lineup for next month's four two-legged playoffs will contain some big teams, whatever happens on Tuesday.
It's likely that Portugal, France and Ukraine will be joining Sweden and Croatia in the playoffs but the three other qualification spots aren't quite so clear-cut.
In Group B, four teams could mathematically finish second, although Bulgaria is favourite to do so if it beats the Czech Republic at home. Third-place Denmark is level on points with Bulgaria, but has a goal difference 7 behind its rival going into its home match against Malta.
In Group D, Turkey and Romania are level on points and battling it out for second behind the Netherlands. Turkey has a goal difference four better than its rival but finishes against the Dutch. Romania has a much easier last match, at home to Estonia.
In Group E, it's a straight fight between Iceland and Slovenia to finish behind Switzerland. Iceland holds a one-point advantage and plays away to Norway. Slovenia travels to Switzerland.
Only eight of the nine second-place finishers go into the playoffs and as it stands, Bulgaria or Denmark is the team set to miss out.