A personal view of pharmacology.

This essay is an account of the author's experience in trying to interpret the action of drugs as seen in in vitro bioassays. The central theme is how the development of simple mathematical models has assisted in the interpretation of drug actions. Starting from encounters with partial agonists, the essay describes the development of an operational model of agonist activity, the significance of receptor distribution, the analysis of indirect competitive antagonism and various two-receptor systems, followed by examples of pharmacological resultant activity. Analyses of tissue and species variations are described. The essay ends with an assessment of the future of bioassay in pharmacology.