Reference is made to little known early work relating egg production in urinary schistosomiasis to muscular exertion. A standard technique for counting eggs in urine is descriptionbed. The effect on egg production of Miracil D, a new drug for the treatment of schistosomiasis, is reported. The importance of examining specimens of urine passed soon after physicalexertion, involving the use of the lower abdominal musculature, is stressed. Warning is made of the danger of missing the diagnosis of urinary schistosomiasis by examining early morning specimens of urine.