As a result of the rather frequent occurrence of crystalluria and hematuria following the use of sulfathiazole and sulfadiazine, an effort has been made to find a sulfonamide derivative of comparable therapeutic potency with less tendency to produce crystals in the urinary tract. This problem is of special importance to our armed forces stationed in warm climates where it is exceedingly difficult to maintain a satisfactory urinary output. Sulfamerazine (2-sulfanilamido-4-methylpyrimidine) has been investigated because of its greater solubility as compared to other pyrimidine derivatives.1Welch and his co-workers2found that sulfamerazine and its acetyl derivative were approximately 20 per cent more soluble than the respective forms of sulfadiazine in both water and urine. Additional studies by Welch and his coworkers,2Goodwin and his co-workers,3and Murphy and his co-workers4indicated that sulfamerazine was more rapidly and completely absorbed from the gastrointestinal tract and also that