The mucosal surface of the human foreskin from newborns shows a propensity to be colonized by pathogenic bacteria. Bacteria with P fimbriae and type 1 fimbriae adhere. However, hydrophobic interaction as well as electrostatic charge appear to be as important in this adherence as are fimbriae. Since bacterial adherence has been shown to precede urinary tract infection in female patients it is assumed that this adherence to the foreskin in male patients also may be necessary before initiation of the disease. The high incidence of urinary tract infection in uncircumcised male patients combined with these findings of adherence of pathogenic bacteria to the mucosal surface of the foreskin, thus, would seem to be related. Prevention of urinary tract infection and acute pyelonephritis in male neonates then may require either circumcision or the prevention of bacterial adherence to the human foreskin.