A computer program written in extended BASIC (BIICAC) is described for analysis of radioimmunoassay and competitive protein binding assay data. This method uses logit and log transformations to obtain a linear dose responsive curve, followed by unweighted and iterated weighted least squares regression analysis (similar to probit analysis). The standard curve is plotted by computer, and potency estimates and confidence limits are obtained for unknowns. This program has been used successfully in a fully automated data processing system using a time-sharing computer service.1