The bacteriochlorin-mediated PDT effects on melanoma tumors were investigated in correlation with its biodistribution. The pharmacokinetics of the photostable 5,10,15,20-tetrakis(2,6-dichloro-3- N - ethylsulfamoylphenyl)bacteriochlorin was determined in DBA mice bearing S91 melanoma tumors at different time intervals (2 h–72 h) after i.p. injection of a 10 mg kg 1 drug dose. PDT efficacy was maximal when irradiation was performed 24 h after i.p. administration, and led to the complete disappearance of tumors for nearly 2 months. Compared to the analogue sulfonated compound, the median tumor growth delay with respect to the control group increased from 27 to 44 days. This improvement is attributed to the higher stability, higher absorption in the NIR, amphiphilicity, and better selectivity of the sulfonamide bacteriochlorin.