Few laboratories are equipped to perform the various procedures which may be needed for the diagnosis of spirochetal jaundice (Weil's disease; spirochetosis icterohemorrhagica). Larson,1 in making a survey of leptospirosis among wild rats, concluded that multiple diagnostic methods should be employed since no single test always gave positive results in a sizable proportion of cases. Rather characteristic lesions in striated muscle in some cases of Weil's disease have been mentioned by Pick2 and Jeghers, Houghton and Foley.3 This report deals with lesions encountered in 16 biopsy specimens from muscles of the calf of 7 patients with Weil's disease seen recently at Grady Hospital. REPORT OF CASES One patient (case 7) was a white man, while the others were Negroes. All had a history of exposure to rats. Two patients (cases 1 and 5) worked as poultry dressers. One patient (case 2) was a fish cutter, 1 (case 4) had been