In order to study the relationship between hrmolysin / ashesins of Escherichia coli and occurrence of urinary tract infection ( UTI), the capacity of 570 isolated E.coli in agglutination of human or guinea pig erythrocytes and their lysis were tested. These isolates were obtained from the urine of patients with bacteriuria and from the stool of healthy people. Three patterns of hemagglutination were recognised; 1) mannose sensitive( MS); agglutination of guinea pig erythrocytes 2) mannose resistant ( MR); agglutination of human erythrocytes, 3) no agglutination. The results indicated that the lytic capacity of isolates producing UTI, is much more than that of fecal flora. Furthermore, it appears that isolates from urine cultures, particularly, the agents of pyelonephritis were predominantly of the MR hemagglutinin type.