The computer program NCOMP performs noncompartmental analysis of pharmacokinetic data obtained from iv bolus, continuous infusion, and oral modes of administration. Integration of area-under-the-curve and area-under-the-first-moment-curve is done by either Lagrange polynomials or the hybrid method of Purves, which uses parabola-through-the-origin and log trapezoidal algorithms. Written for Microsoft Windows, NCOMP is designed to be used in conjunction with a spreadsheet program for graphical display and handling of data. NCOMP interactively aids the user in determining how best to extrapolate the areas to time infinity and in estimating the time zero concentration for iv bolus data.