Digitoxin was 86% bound to plasma from uremic patients while plasma from healthy volunteers bound 90%. The binding of diphenylhydantoin (DPH) was also depressed in uremia. We isolated albumin by curtain electrophoresis from plasma of uremic and normal individuals. Apparent association constants of albumin for DPH were: uremic 2.8 × 104, normal 6.0 × 104. Disc and curtain electrophoretic behavior of albumin from normal and uremic patients were similar. Isoelectric focussing revealed differences in micro-heterogeneity among albumins isolated from normal volunteers or uremic patients and commercial crystalline human serum albumin.