In a prospective controlled multicenter study, the prophylactic effect of gentamicin-containing bone cement on postoperative infections in total hip arthroplasties was compared with that of systemically given antibiotics; 812 arthroplasties were randomly assigned to an antibiotic and 821 to a gentamicin-cement group. When the patients had been followed for a period of one to two years, 13 deep infections were diagnosed in the antibiotic group and three in the gentamicin-cement group. The difference was statistically significant.