In this paper the base catalyzed condensation reaction of 2-thiobarbituric acid with some aromatic aldehydes resulting in the formation of 5-arylidene-2-thiobarbituric acids is described. The condensation reaction of 2-thiobarbituric acid was carried out with 4-methoxybenzaldehyde, 4-ethoxybenzaldehyde, 4-benzyloxybenzaldehyde, and 1-naphthaldehyde using morpholine as a catalyst.