Swedish Grandmaster (1982) and Swedish Champion 1992.
Best results: Malmo 1979, 1th ; Hradec Kralove 1979-80, 1th ; Nis 1981, 1th ; Eskjo 1982, 1th ; Helsinki 1983, 1st; Hastings 1983-84 1-2nd ; Esbjerg 1984, 2-3nd ; Cannes 1986, 2nd , Copenhagen 1988, 1th ; Oslo 1988 and 1989, 1th ; Hallsberg 1996, 1th , Open de Catalunya Escacs Club 2009, 1th .
Karlsson played in four Olympiads between 1980 and 1990.
The author of Svenska Schacktriumfer (1992).
Peak rating: 2550 in 1985.