Several 1-alkyl-4-piperidylidene analogs were synthesized and tested for inhibitory activity on the compound 48/80-induced release of histamine from mast cells. 4-(4-Isochromanylidene) (12b) and 4-(diphenylmethylene) (14) derivatives of 1-benzylpiperidine were much more active than the lead compounds, 1-benzylspiro [isochroman-piperidines] (1b and 2b).