A series of 37 patients with cutaneous metastases of breast carcinoma were treated with photodynamic therapy (PDT) to the chest wall; decreasing doses of photofrin II and increasing light doses were used in order to test drug/light dose reciprocity and determine the lowest effective dose of photofrin II. 5 patients (13.5%) achieved a complete response, 13 (35.1%) demonstrated partial responses and 19 (51.4%) showed no benefit. The extent and type of recurrent disease were strong determinants of the likelihood of response. Minimal and nodular disease responded well to PDT (5/5 complete responses); partial responses were seen in 11/20 (55%) of patients with disease of moderate extent. No patient with extensive erythema derived any benefit (0/5), and only 2/12 (17%) patients with advanced nodularity showed a partial response. Reduction in photofrin dose to 0.75 mg/kg with reciprocal increases in light dose to 182 J/cm2 did not impair treatment efficacy.