['To investigate whether the early use of phosphodiesterase inhibitors (PDEIs) after brachytherapy (BT) is associated with better erectile function, as of men potent before BT 38-70% have erectile dysfunction afterward.', 'We evaluated a prospectively created database of 2500 patients who had had BT at our institution since 1992. We measured baseline age, cancer stage, Gleason grade, prostate specific antigen (PSA) level at diagnosis, implant type, use of neoadjuvant and adjuvant hormonal suppression therapy, use of external beam radiotherapy in conjunction with interstitial therapy, and follow-up PSA levels. Men were stratified by their use of PDEIs at <1 year (early group) or >1 year after implantation (late group). We excluded all men who did not have baseline Sexual Health Inventory for Men (SHIM) scores and at least one follow-up SHIM score; the latter were obtained at 6-month intervals after BT. Data were analysed using the Mann-Whitney U-test.', 'In all, 210 men met the inclusion criteria; 85 began using PDEIs within a year of BT, and 125 started after a year. The mean time to PDEI use was 191 days in the early and 595 days in the late group. The median age was 62 years in the early and 63 years in the late group (P = 0.02). Baseline Gleason scores did not differ, nor did PSA levels between the groups. Of men in the early group, 48% received neoadjuvant and/or adjuvant hormonal suppression therapy, vs half of men in the late group. Baseline SHIM scores were not significantly different, nor were scores at the first two follow-up assessments, but the scores at 18-36 months after BT were significantly different.'] Does early use of a phosphodiesterase inhibitor after brachytherapy restore and preserves erectile function?