Summary

First Round
The format of the competition changed from 1982: 24 teams qualified, divided into six groups of four (A through F). The top two teams and the four best third place finishers from the six groups advanced to the knockout round of 16 teams.
The first round of the finals began in Group A, where Italy were held 1-1 by a dour but spirited Bulgaria side. Meanwhile, Argentina had little trouble beating South Korea 3-1, with Diego Maradona in awesome form. Italy and Argentina drew 1-1 in a bad tempered affair, which saw Maradona and Alessandro Altobelli scoring. South Korea and Bulgaria also drew 1-1 in a Mexican downpour. The final set of matches saw Argentina beating Bulgaria 2-0, and Italy narrowly defeating South Korea 3-2 in an exciting match.
Group B was straightforward for the hosts, Mexico as they beat a defensive Belgium side 2-1, and despite being held 1-1 by Paraguay, they won the group after a further win over minnows Iraq, 1-0. Paraguay and Belgium also progressed after both beating Iraq and drawing with each other. Group C was an interesting contest as it pitted a strong Soviet Union side against the reigning European Champions France. They drew with each other in a fine match 1-1, which was notable for a fantastic goal by Vasili Rats. France made hard work of beating Canada 1-0, but progressed in 2nd place after beating a demoralised and aging Hungary, 3-0. Hungary had earlier lost 6-0 against the Soviet Union.
Group D saw Brazil start sluggishly against Spain, winning 1-0, although Spain had a legitimate goal disallowed. Northern Ireland began their campaign with a draw against Algeria. Northern Ireland were then beaten narrowly by Spain before being simply outclassed by Brazil 3-0 in their final match. This match saw a great goal from Josimar on his debut and was also the final time Pat Jennings would play for Northern Ireland. Spain qualified along with Brazil after defeating Algeria 3-0.
Denmark, stormed through Group E, highly dubbed the group of death with a 100 per cent record. They beat Scotland 1-0 in their first game, then hammered Uruguay 6-1, with Preben Elkjær Larsen hitting a hat-trick. But Denmark's most impressive result were when they beat one of the favourites to win the tournament, West Germany, 2-0 thanks to a Jesper Olsen penalty and a goal from John Eriksen. After losing to Denmark, Scotland took the lead against West Germany thanks to a Gordon Strachan goal, but the West Germans fought back to win 2-1. And after a violent 0-0 draw against Uruguay, the Scots were eliminated from the tournament. West Germany went through to the second round with the strength of a win and a 1-1 draw with Uruguay, who also qualified on just two draws.
Morocco topped Group F after holding both Poland and England to goalless draws, and then playing some marvellous football to beat Portugal, 3-1. By doing so, they became the first African team to reach the second round, and obviously the first to win a group. England looked to be in trouble after losing 1-0 to Portugal and then drew with the Moroccans. But in their last first-round game, a first-half Gary Lineker hat-trick helped them beat Poland 3-0. Poland had previously beaten Portugal, and in the end the Portuguese were the only team from Group F to be eliminated in the first round.