Pituitary hormone release after electroconvulsive therapy (ECT) may provide important information about certain of the effects of ECT on neurotransmitter function. Previously we quantified pituitary hormone release by the increase in the area under the hormone concentration/time curve. Swartz has rightly pointed out that this method ignores the rate of elimination of hormone and cannot be a measure of total hormone released. Swartz has proposed a kinetic model of hormone release, and in this paper we assess the reliability of parameters derived from it when applied to our own data on the effects of ECT on the release of prolactin and oestrogen-stimulated neurophysin. The deviations between observed and predicted values were small when only five post-ECT samples were used. Contrary to expectations, the goodness of fit did not improve when the number of sampling points was increased to nine after ECT. It was possible to fit a unique curve to the observed data in only 28 of 54 data sets. The reasons for these findings are discussed.