In a national surveillance system study, the infection rate following cerebrospinal fluid shunt surgery was 4.1% (95% confidence interval, 3.36%-4.92%). Cases of infection were more common in children than in adults (4.85% vs 3.24%; P = .04) and occurred sooner after surgery in children than in adults. A wide variation in compliance with antimicrobial prophylaxis was observed between 21 participating medical centers.