Czechoslovakia's Miloslav Mecir and Tomas Smid upended Wimbledon champions Ken Flach and Robert Seguso in four sets yesterday to win the $200,000 Masters Doubles tennis championship at Albert Hall in London.

The Czechoslovakians gained their fifth title of the year and a check for $72,000 after winning, 6-4, 7-5, 6-7, 6-3, in 3 hours 5 minutes.

On the way to the final, Mecir and Smid were the only team to go through five matches unbeaten. Twice during the round-robin event they beat the defending champions, Stefan Edberg and Anders Jarryd, who are likely to be Sweden's doubles team in next week's Davis Cup final against India in Gothenburg.

The Czechoslovakians exploited the Americans' mistakes, especially on Flach's fragile two-handed backhand. From the moment Seguso's serve was broken in the opening game, Mecir and Smid had a firm hold on the match, which at one stage looked like it would go no further than the minimum three sets.

Seguso was adamant that his side had chances to win, however. "We definitely had more chances to break than they did. The trouble was, we didn't take them," he said. "They are a good team, but we all came out flat for the final. We came out stale, they came out staler."