Twenty-three cases of porcine cystitis and pyelonephritis were examined bacteriologically. Eubacterium suis was found in 21 cases. The isolation of large numbers of Escherichia coli in the upper urinary tract was associated with linear renal scarring. An unidentifiable streptococcus and Enterococcus faecalis were isolated from a case of purulent ureteritis, pyelitis and pyelonephritis. The bacterial flora from cases of cystitis and pyelonephritis was different from that isolated from sows with asymptomatic bacteriuria.