The appearance of cloudy dialysate fluid in combination with the clinical manifestations of peritonitis usually heralds infectious peritonitis. Diagnosis is readily established in most cases by routine culture of the turbid dialysate. However, an occasional patient presents with culture-negative, cloudy dialysate. After ruling out atypical infectious etiologies, a diverse set of aseptic causes remains in the differential diagnosis. Herein we review these causes and suggest an organizational scheme, based on identifying the cellular or noncellular constituent producing the dialysate turbidity, to facilitate appropriate diagnostic and therapeutic interventions.