This report is about three cases of digestive cancer with psoriasis vulgaris. The first patient, a 71-year-old man, had psoriasis vulgaris associated with rectal cancer. After a successful resection of rectal cancer, his rash was reduced. The second patient, a 63-year-old man, had psoriasis associated with synchronous double cancer of the stomach and rectum. After a simultaneous radical resection, his rash was improved, probably due to a successful treatment with topical steroid ointment prior to the surgery. The third patient, a 52-year-old man, had psoriasis associated with gastric cancer. His rash was not reduced after a radical surgery, and did not become worse on recurrence of the cancer. Eighteen cases of internal malignancies with psoriasis vulgaris have been reported in Japan. Regarding our experience and investigated references on this matter, we believe that visceral malignancies might induce or worsen psoriasis vulgaris.