In recent years an increase of severe invasive infections and toxic shock syndrome (TSS) with beta-haemolytic Group A streptococci (Streptococcus pyogenes, GAS) has been reported from North-America and North-Western Europe. In the spring of 1992 several reports of cases suggested that this epidemic wave might have reached the Netherlands. Subsequently a national surveillance was initiated. Between 1-7-1992 and 31-12-1993 GAS-isolates from 440 patients were sent to the public health laboratory for typing ; from 220 of those 440 patients (50%) demographic and clinical data were obtained. In 132 of those 220 patients invasive infection with GAS was clinically and bacteriologically documented. Forty-one of those 132 patients (31%) suffered from TSS. Cases were not associated with a particular geographical region. The incidence of TSS was highest in the age groups of 30 to 50 years and in individuals older than 60 years. Mortality associated with TSS was 51%. In the majority of cases (61%) no underlying diseases were reported. In 20 of the 41 TSS-cases no obvious portal of entry for infection was detected. In the remaining cases diverse primary local infections were observed. In 30% of cases fascitis necroticans and/or myositis was present. In 11% of cases TSS was acquired in the hospital. Type T1/M1 was the etiological agent in 31% of all (440) patients ; none of the other 19 different T/M- types found contributed more than 10%. T1/M1 was strongly associated with TSS (22 of 41 cases, 54%). Ninety-two percent of the T1/M1 strains contained the bacteriophagelocated gene for exotoxine A. RFLP analysis of the M1 gene of T1/M1 strains revealed one single pattern.