Identification of beta hemolytic streptococci (BHS) as group A or non-group A on the basis of bacitracin sensitivity rather than Lancefield serogrouping may lead to misidentification of the pathogen. In four recent cases of endocarditis due to BHS, the pathogens initially were identified as group A; Lancefield serogrouping showed all four to be group G. All four patients presented with a syndrome characteristic of acute bacterial endocarditis. Review of all cases of endocarditis at our institution for the past five years showed none due to group A BHS. In 166 previously reported cases of endocarditis due to BHS, 68 pathogens were serogrouped: 53 belonged to groups B, C, G, or H; only five were group A. Our four cases and review of the literature demonstrate the need for Lancefield serogrouping in serious beta hemolytic streptococcal infections, rather than reliance on bacitracin sensitivity.