A series of 1-benzoyl- and 1-phenylisoquinolineacetic acid derivatives was prepared and tested for antiinflammatory activity. The most potent compound synthesized, 1-(4-chlorophenyl)-3-isoquinolineacetamide, was as active as phenylbutazone in the Evans blue carrageenan-induced pleural effusion assay but inactive in the adjuvant-induced arthritis model of chronic inflammation.