Highest Sonas Performance Ratings

Men

*Karpov 2899 - Linares 1994, 11/14 84.6%
Fischer 2887 - Candidates Semi-final vs. Larsen, Dallas 1971 +6 100%
Lasker 2882 - World ch. vs. Steinitz, Moscow 1896 12.5/17 73.5%
Kasparov 2881 - Tilburg 1989 12/14 85.7%
Lasker 2878 - London 1899 21.5/26 82.7%
Lasker 2876 - World ch. vs. Marshall, USA 1907 11.5/15 76.7%
Kramnik 2874 - BGN World ch. vs. Kasparov, London 2000 8.5/15 56.7%
Karpov 2873 - World ch. vs Kasparov, Moscow 1984-5, 25/48 52.1%
Fischer 2870 - Candidates Quarter-final vs. Taimanov, Vancouver 1971 +6 100%
Tal 2869 - Candidates, Bled/Zagreb/Belgrade 1959 20/28 71.4%
(*Recently Grischuk brak this record in Europian CHamiopnships 2007)


Women

Judit Polgar 2778 - Madrid 1994
Judit Polgar 2760 - Wijk aan Zee 2003
Judit Polgar 2746 - Polgar-Piket match, Aruba 1995
Judit Polgar 2739 - Linares 1997
Sofia Polgar 2735 - Rome 1989
Judit Polgar 2733 - Sicilian, Buenos Aires 1994
Judit Polgar 2728 - Dos Hermanas 1993
Judit Polgar 2719 - Donner Memorial 1995
Judit Polgar 2717 - Hastings 1992
Judit Polgar 2715 - Dos Hermanas 1995

Susan Polgar and Maia Chiburdanidze are the next two to appear on the list somewhat further down. Both achieved ratings of 2677 at Aruba 1992 and Banja Luka 1985 respectively. (Source : Jeff Sonas's Chessmetrics Site May 2005).
For comparison, here are some of the highest Elo performance ratings for FIDE sponsored events since 1970.

1971 Candidates semi-final, Dallas, Fischer-Larsen +6 3060
1971 Candidates 1/4-final, Vancouver, Fischer-Taimanov +6 3020
2001 Europe v. Asia Rapid, Batumi, Kasparov 3017
1994 Linares, Karpov 11/13 84.6% 2942
2000 Rapid Frankfurt, Anand 2941
2002 Bled Olympiad, Kasparov 2933
1989 Tilburg, Kasparov 2913
1989 Belgrade, Kasparov 2907
2002 Essen, Zvjaginsev 2905
1998 Pamplona, Morozevich 2904
1997 Linares, Kasparov 2884
2000 Sarajevo, Kasparov 2881