15596 Purpose: Assess erectile function before and after prostate brachytherapy. Materials and Methods: A total 241 patients were treated with permanent I-125 prostate brachytherapy for T1 and T2 adenocarcinoma of the prostate. A retrospective chart review was undertaken to assess erectile function before and after treatment using the scoring system of, 1- complete inability to have erections, 2 - can sometimes have erections sufficient for intercourse with or without medication, and 3 - has normal erectile function. Pretreatment testosterone levels were reviewed for correlation with pretreatment erectile function. Results: The median age was 68. At presentation, the median age of patients with erectile scores of 1, 2 and 3 was 70, 67 and 67 respectively. The median time of follow-up was 48 months. Pretreatment erectile function assessment revealed scores of 1 in 28%, 2 in 27% and 3 in 45% of patients. Median pretreatment testosterone levels were 296 ng/dl in the patients with pretreatment score of 1 compared to 360 ng/dl in patients with a score of 2 and 370 ng/dl in patients with a score of 3. The normal testosterone range for this age group is 165 ng/dl to 830 ng/dl. After 12 months erectile function assessment revealed scores of 1 in 29%, 2 in 42% and 3 in 29% of patients. After 24 months erectile function assessment revealed scores of 1 in 30%, 2 in 41% and 3 in 29% of patients. After 36 months erectile function assessment revealed scores of 1 in 32%, 2 in 45% and 3 in 23% of patients. After 48 months erectile function assessment revealed scores of 1 in 39%, 2 in 36% and 3 in 25% of patients. After 48 months, the median age of patients with erectile scores of 1, 2 and 3 was 75, 69 and 66 respectively. After 60 months erectile function assessment revealed scores of 1 in 32%, 2 in 47% and 3 in 21% of patients. After 72 months erectile function assessment revealed scores of 1 in 24%, 2 in 52% and 3 in 24% of patients. 49% of patients were given sildenafil, vardenafil, or tadalafil to improve erectile function. Conclusion: The rate of potency preservation in this cohort declined in an expected manner after permanent brachytherapy for prostate cancer. No significant financial relationships to disclose.