Swelling, pale and bilateral lesions on the thorax of crayfish (Astacus leptodactylus) were observed in Egirdir Lake in between 1990-2000. Acremonium sp. was isolated from gill lesions of 120 crayfish. Branched septate hyphae were seen following isolation on glucose yeast-extract penicillin-streptomycin (GY-PS) agar. Conidia were oblong and usually single celled. Saprolegnia sp. and Vibrio sp. were also isolated as secondary infectious agents from some lesions. Although no mortality was associated with these lesions, this condition can have a negative effect on the market value of crayfish.