We report the results of sacrified photopatch testing in 3 patients with photosensitivity to lomefloxacin, a new quinolone: antibacterial agent introduced onto the Japanese market in April 1990. The patients developed pruritic eczematous lesions on sun‐exposed areas 5 days to 3 weeks after they had started taking lomefloxacin. 2 cases reacted positively to lomefloxacin on scarified photopatch testing down to 0.1% pet., arid 1 patient down to 10% pet One of them also showed positive reactions on conventional photopatch testing; Scarified photopatch testing with 7 other pyridone carbonate derivatives in 2 of the 3 cases, however, did not show any positive reactions patch and scarified patch testing were negative in all patients. The clinical course, clinical and histological findings and results of skin tests in these patients suggest that photoallergic mechanisms arc involved. This is the 1st report of positive reactions on scarified photopatch testing, which appears to be a useful method of detecting the causative drug in drug‐induced photosensitiv