A highly sensitive and selective spectrophotometric method is developed to measure micro amounts of albumin. The proposed method is based on the fact that zirconium(IV)-Xylenol Orange complex fades in the presence of albumin. In the concentration range of 0.1-0.9 mu g cm(-3), human serum albumin obeys Beer's law and shows an effective molar absorptivity of 8.4 x 10(7) dm(3) mol(-1) cm(-1) at 605 nm.