To evaluate the early morbidity of palladium 103 ( 103 Pd) prostate brachytherapy.Thirty-two patients with Stage A or B prostate carcinoma were implanted transperineally with 103 Pd using transrectal ultrasound and fluoroscopy between May 1990 and December 1992. Patients were subsequently followed to evaluate for morbidity and possibility of migration of the implanted seeds into the lungs.The median follow-up time was 20 months (range, 2 to 45 months). The major acute toxicity of the procedure, dysuria, was seen in 88% of the patients. Although this was generally grade 1 or 2 and transient, grade 3 or 4 toxicity occurred in 18% of patients. Mild rectal symptoms (transient diarrhea, rectal bleeding) occurred in 19% of patients. Sexual functions could not be evaluated. Seven of the 3213 total seeds implanted (0.2%) were found to have migrated to the lung in 6 of 30 (20%) patients having a postoperative chest radiograph. This did not cause any clinical problems. 103 Pd prostate brachytherapy is generally associated with only mild or moderate urinary and rectal symptoms, and the incidence of severe complications is low. Further follow-up is required to evaluate the efficacy.