We studied the effect of combining intracavernous injection and an external vacuum in 10 men with erectile dysfunction who previously failed attempts at treatment with either method as single therapy. We measured the length, circumference and buckling pressure of the penis at baseline, after applying negative pressure (250 mm. Hg for 2 minutes), 15 minutes after intracavernous injection of 60 mg. papaverine or 30 mu g. prostaglandin E1 and after combining both modalities. No patient achieved adequate rigidity (defined as a penile buckle pressure greater than 450 gm.) with single therapy. The mean buckle pressure using vacuum alone was 125.0 +/- 53.6 gm. After intracavernous injection the mean buckle pressure was 117.0 +/- 38.3 gm. In contrast, all 10 subjects responded to combination therapy with a mean buckle pressure of 565.0 +/- 56.8 gm. (p <0.0001). After 10 months of followup 3 subjects were still using the combination and were satisfied with the erectile response, I found that he no longer needed the addition of external vacuum after using combination therapy for 3 months, 1 used the combination for 9 months and then stopped because of an intervening acute illness, 1 lost the partner due to death, 2 found combination therapy to be too cumbersome and 2 were lost to followup. We conclude that external vacuum devices can augment a partial response to intracavernous injection and the combination may be an alternative treatment before intrapenile prosthesis implantation.