The capability of two commercial systems was studied for microbial detection in dialysis effluents from patients on continuous ambulatory peritoneal dialysis (CAPD). Two methods of processing dialysate from patients on CAPD were compared: (a) direct inoculation of 10 ml of dialysate into a single bottle broth culture system (Signal; Oxoid, U.S.A., Columbia, Maryland) and 5 ml into each of two BACTEC blood culture bottles (Johnston Laboratories, Towson, Maryland); and (b) centrifugation of 50 ml of dialysate and culture of the sediment in an Oxoid bottle. Of the 196 specimens cultured, 99 (51%) yielded growth. Recovery rates of significant isolates were 95% for the BACTEC system, 89% for the Oxoid system, and 88% for the centrifugation-Oxoid system. Recovery of eight isolates from the Oxoid system was by subculture rather than a visual "signal." The Oxoid system is a practical, cost-effective, alternative culture method for effluents from CAPD patients in laboratories not having access to the BACTEC system.