This paper describes a reliable multiple sample Evans Blue dye dilution technique and a Pascal program which computes plasma and blood volume on the basis of this technique. The program performs needed corrections and dye disappearance curve fitting. It provides menu-driven facilities for data correction, graphic display of the dye disappearance curve, and print-out of all the involved data. Means +/- S.E.M. for three plasma volume determinations in each of six resting subjects were: 3239 +/- 96 ml, 3189 +/- 81 ml, and 3187 +/- 102 ml. The differences were not statistically significant.