A structure activity study was conducted on two important members of the styryl class of tyrosine-specific protein kinase inhibitors to examine relative roles which the aryl rings and vinyl side chains play in their inhibitory activity. The ability of four analogs (1a-d) to inhibit autophosphorylation of epidermal growth factor receptor (EGFR) and p56lck tyrosine kinases was examined, with results showing that both the pattern of aromatic hydroxylation and the type of side chain functionality can greatly influence both selectivity and potency.