Forty-nine clinical isolates of group B streptococci (GBS) were correctly grouped from broth culture by the Fluoro-Kit immunofluorescence test. A further 82 beta-haemolytic streptococci of groups A, C, D, F, and G were tested and gave no cross-reactions. The test was simple to perform and gave clear results. The Fluoro-Kit reagents, however, failed to detect GBS in 21 (51%) of 41 smears of rectal or vaginal swabs from pregnant women from which GBS were subsequently grown. Thirty-two (20%) of 159 culture-negative swabs gave positive immunofluorescent reactions.