Serum lactate dehydrogenase (LD) isozyme studies are widely used in various clinical conditions and there are well documented cases of extra LD bands in patients with various diseases. However, it is only in recent years that urinary LD isozyme patterns have been utilized for differential diagnosis of urinary trace infections and to our best knowledge extra LD bands in urine have not been reported in the literature. In recent two years, we have experienced urinary extra LD bands in 4 patients with clinical and laboratory evidence of urinary tract infections. Two of these patients had spesis and one was in postoperative state of prostatic carcinoma and nother one had recurrent urinary tract infection. These extra LD bands showed similar electrophoretic mobility, moving anodal to LD1 fraction on cellulose acetate electrophoresis. The origin and significance of these extra LD bands in urine is not known, and some of the possibilities are discussed.