A case of Lactobacillus casei endocarditis that occurred on a Carpentier-Edwards porcine valve is reported. A review of the literature, which yielded 23 other reports of endocarditis due to this organism, suggests that Lactobacillus is a rare cause of endocarditis. Typically, it occurs in a patient with preexisting structural heart disease (20 of 24 [83%]) and often with some form of recent dental infection or manipulation (18 of 24 [75%]). Six (25%) of 24 patients died of this infection; however, only one (5%) of 19 who were treated with adequate antimicrobial therapy died. The response to antimicrobial therapy was better in the more recent cases. Of those 18 patients who completed a full course of therapy, seven (39%) experienced a relapse; five of these were cured of their infection with a second course of antimicrobial therapy, which usually included higher doses of intravenous penicillin. Our case represents the second reported case that required surgical intervention for cure. Embolic phenomena occurred in 10 (42%) of 24 cases. Various combinations of antibiotics have been successful in achieving cure; however, at present, high-dose penicillin (greater than 25 million units/day) in combination with an aminoglycoside for a period of six weeks appears to be the optimum therapy.