Department of Pharmaceutical Chemistry, College of Pharmacy, Sri Ramakrishna Institute of Paramedical Sciences, Coimbatore-641 044, Tamilnadu, India E-mail : kmano1975@rediffmail.com Manuscript received 22 October 2008. revised 7 April 2009, accepted 19 May 2009 A series of new thiazolidin-4-ones (3a-j), 5-carboxymethyl-4-thiazolidinones (4a-1) have been synthesised via the condensation of 4-methylcoumarinyl-7-oxyacetic acid [(substituted phenyl)methylene]hydrazides (2a-1), with thioglycolic acid and thiomalic acid respectively. The compounds (2a-1) were synthesised from 4-methylcouhlarinyl-7-oxyacetic hydrazide using various aromatic aldehydes. The structure of all synthesised compounds has been determined by spectral methods. The compounds were screened for their antibacterial activity against S. aureus and B. subtilis bacteria.