OBJECTIVES: To determine the antibiotic susceptibility and plasmid profile of all Neisseria gonorrhoeae strains (PPNG and non-PPNG) isolated from May 1995 to March 1996 in Lok Nayak Hospital, New Delhi, India. METHODS: The agar plate dilution method was used to determine the minimum inhibitory concentration of five antimicrobials including norfloxacin and ceftriaxone which are most commonly used for treatment of gonorrhoea in Delhi. Isolates were screened for production of penicillinase by paper acidometric method and plasmid analysis of PPNG and non-PPNG was carried out by agarose gel electrophoresis. RESULTS: 50 consecutive isolates of N gonorrhoeae were studied, 8% among them were found to be PPNG while 28% were highly resistant to tetracycline (TRNG). Reduced susceptibility to norfloxacin (MIC > or = 1 microgram/ml) was observed in 12% of all isolates. All PPNG harboured the 4.4 MDa beta lactamase plasmid along with the 25.2 MDa tetracycline resistance plasmid. Norfloxacin resistance (MIC > or = 1 microgram/ml) was present in 28.5% of TRNG but only in 5.5% of the other gonococcal isolates. CONCLUSIONS: Results of this study clearly demonstrate that antibiotic resistant gonococcal strains of different clones are frequently found in New Delhi. Continued surveillance of susceptibility to currently prescribed antimicrobials and epidemiological studies are essential to prevent treatment failures leading to further spread of resistant strains.