The histopathology of acute fin rot disease in summer flounder, Paralichthys dentatus, from the New York Bight is described. Grossly, caudal and dorsal fin lesions appeared ragged or frayed with no evidence of resolution. Microscopically, there was epidermal and dermal necrosis, congestion, edema, focal and diffuse hemorrhage, and Zenkers necrosis of underlying muscle. Gram-negative bacteria were present in the fin tissues as well as in heart muscle and liver parenchyma. The inflammatory response consisted mostly of macrophages. The significance of the acute disease in summer flounder is discussed in relation to the etiology of fin rot disease in winter flounder from the Bight.