One adverse effect of PUVA therapy is the development of severe dermatitis. Only a few cases of photoallergy to psoralens during PUVA therapy have been reported. We describe herein a patient with photoallergic dermatitis induced by PUVA with 8-methoxypsoralen(8-MOP). A 38-year old woman with generalized vitiligo had acute pruritic exanthematous maculopapular lesions in the treated areas after PUVA therapy with 8-MOP. A patch test and photopatch test were performed with 8-MOP, 5-MOP, and 4,5,8-trimethylpsoralen(TMP). The patch test carried out with these psoralen derivatives were all negative, but the photopatch test showed a positive reaction to 8-MOP. The patient consequently had PUVA therapy with 5-MOP and she had no further experience of a photoallergic reaction.