Twenty-five percent of the patients receiving peritoneal dialysis and 5% of those receiving hemodialysis switched to the other dialysis type during follow-up. Patients starting treatment with peritoneal dialysis appeared healthier than did those starting treatment with hemodialysis. Also, more of them were high school graduates, were married, and were employed. Analyses that adjusted for these differences found statistically significantly higher risks for death among patients receiving peritoneal dialysis compared with those receiving hemodialysis during the second, but not first, year of dialysis.