Several substituted 2-aminophenylacetic acid derivatives were prepared and tested for in vitro prostaglandin synthetase inhibition activity and for in vivo antiinflammatory activity. The 2-amino substituent is beneficial to potency in the inhibition of prostaglandin synthetase for the 3-phenoxy, 4-phenyl, and 3-benzoyl series, but only the 3-benzoyl series shows increased antiinflammatory potency in the in vivo assay.