1-Imidazolylalkyl-substituted di- or tetrahydrobenzo[b]thiophenecarboxylic acid derivatives and related compounds were synthesized from tetrahydrobenzo[b]thiophene derivatives (1 or 4) in order to study the structure-activity relationships of the inhibition of thromboxane A2 synthetase in vitro. Sodium 2-(1-imidazolylmethyl)-4,5-dihydrobenzo[b]thiophene-6-carboxylate (26) and 2-(1-imidazolylmethyl)-4