Data from 95 adult patients (43 males, 52 females) treated with ventriculoperitoneal shunts during an 8-year period were analyzed to investigate risk factors in shunt surgery. All patients were seen in the authors' department and were grouped according to the cause or type of hydrocephalus. The operating surgeons were divided into two categories: specialists and residents. The shunts were classified as single- (Orbis-Sigma) or multicomponent (Holter or Hakim) systems. Two types of unfavorable events were recognized: complications and shunt malfunction. A total of 143 surgical procedures (implantations and revisions) were performed in the 95 patients; 24 patients had their shunts revised, and there were 13 complications (one fatal, five severe) resulting from the shunt surgery. The following observations were statistically significant: 1) patients with normal pressure hydrocephalus had no complications from shunt surgery; 2) the number of shunt malfunctions was lower in patients with intracranial hemorrhages than in the other groups; 3) residents performed a higher number of inadequate operations than did specialists; and 4) the infection rate was higher among patients operated on by residents. The choice of shunt type, the perioperative use of antibiotics, and the degree of surgical emergency were not correlated with complication or failure rates.