Using molecular modelling, three chemically distinct members of the okadaic acid class of protein phosphatase inhibitors and tumor promoters, okadaic acid, calyculin A and microcystin-LR were fitted together. The molecular modelling results indicate a pharmacophore model consisting of a central cone, containing one conserved acidic group and two potential hydrogen bonding sites, and a non-polar side chain. The binding of the okadaic acid class of compounds to their receptors, the catalytic subunits of protein phosphatases 1 and 2A, causes an inhibition of phosphatase activity resulting in modulation of cellular events controlled by phosphorylation/dephosphorylation mechanisms.