Accepted criteria for the diagnosis of peritonitis in CAPD include: 1. symptoms and signs of peritoneal irritation; 2. a cloudy effluent with white blood cell (WBC) count greater than 100/microliters and; 3. a positive culture. In fact, the earliest suggestive sign of peritonitis is a turbid effluent. However, symptomatology of peritoneal irritation may precede the development of a cloudy fluid. We hereby report on two CAPD patients with culture proven peritonitis whose initial presentation was that of an acute abdomen. Although diffuse rebound tenderness was elicited the initial effluent, after an overnight dwell, was clear with a WBC count of 80 and 70/microliters, respectively. Working diagnoses on admission included a ruptured cyst and a perforated peptic ulcer. Both patients were in line for a laparotomy. After a period of 7 and 12 hours, respectively the ensuing effluents turned turbid with WBC counts of 6,400 and 2,500/microliters. Cultures eventually grew Staphylococcus aureus and Streptococcus viridans. Appropriate antibiotic treatment resulted in full recovery.