Abstract: Kubinyi's bilinear model showing the relationships between biological activity and hydrophobic character in QSAR is derived from McFarland's probability modal. This new model describes non-linear lipophilicity -activity relationships without systematic deviations. The β of the bilinear model is a non-linear term which must be calculated by an iteration procedure. This paper deals with programming Kubinyi's bilinear model for the TI programmable 59 by using the Taylor theorem. The program is rapid and accurate at figures.