In recent years, new quinolones such as ofloxacin (OFLX) and tosufloxacin (TFLX) have been frequently used in the treatment of bacterial enteritis caused by unknown organisms. The agent of first choice for the treatment of Campylobacter enteritis is one of the macrolides, but new quinolones are often administered accidentally to adult patients with Campylobacter enteritis. We have detected quinolone-resistant strains of Campylobacter jejuni (C. jejuni) after the treatment of some patients with new quinolones, and accordingly we reviewed the treatment of Campylobacter enteritis. We experienced 178 adult patients with Campylobacter enteritis from January 1989 to November 1991 at our hospital. From them, we selected 52 patients (32 males and 20 females) in whom stool culture were performed both before and after treatment. The initially administered antimicrobial agent was a macrolide (rokitamycin, RKM) in 6 cases, a new quinolone in 22 cases, and kanamycin (KM) in 24 cases. The new quinolone used was OFLX in 17 cases, TFLX in 3 cases, and norfloxacin (NFLX) in 2 cases. Fifty-one of the 52 C. jejuni strains isolated before treatment were susceptible to OFLX and erythromycin (EM) according to antimicrobial disc susceptibility tests. C. jejuni was eradicated in all patients treated with RKM or KM. However, treatment failed to achieve bacteriological cure in 8/22 (36.4%) patients given new quinolones. In these patients, the strains of C. jejuni isolated before treatment were susceptible to OFLX, but the strains isolated after treatment were all resistant to OFLX according to disc susceptibility tests.(ABSTRACT TRUNCATED AT 250 WORDS)