In light of the correlation between the dialysate to plasma ratio of creatinine (D/P Cr), peritoneal (PD) protein loss and hypoalbuminaemia, peritoneal permeability has been implicated as a risk factor for malnutrition in CAPD patients. However, serum albumin is also affected by hydration which is itself influenced by peritoneal permeability. In a cross-sectional study of 147 CAPD patients we investigated the relationship between peritoneal permeability, PD protein loss and nutritional state. Stepwise regression analysis revealed D/P Cr to be the only significant predictor of serum albumin independent of PD protein loss. No significant relationship was demonstrated between D/P Cr, body fat, lean muscle mass and dietary protein intake. Increased peritoneal permeability does not cause hypoalbuminaemia as a consequence of increased PD protein loss, and does not adversely affect somatic fat and protein status.