Reactions of primaryselenoamides with dimethyl acetylenedicarboxylate afforded 2-aryl-5-methoxy-carbonylmethylene-4,5-dihydro-1,3-selenazol-4-ones in moderate to high yields. Reactions of the primaryselenoamides with acetylenedicarboxylic acid gave 2-aryl-5-carboxymethylene-4-ethoxy-4,5-dihydro-1,3-selenazol-4-ols in moderate yields.