Background: In 1999, the American Brachytherapy Society (ABS) recommended brachytherapy monotherapy (BT) be limited to low-risk prostate cancer, in part because a high-impact 1998 publication suggested that intermediate or high-risk disease had worse outcomes with BT than with external beam radiation (EBRT) or radical prostatectomy (RP). We studied temporal patterns of BT use before and after the 1999 ABS published guidelines as compared with 4 other treatment options. Methods: A retrospective analysis was performed of all men with T1c-T3cN0M0 prostate cancer treated definitively in the United States from 1990 to 2011 in the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry. Logistic regression was used to estimate adjusted odds ratios (AOR) comparing BT use with other treatment groups between the 1990-1998 and 1999-2011 periods, controlling for age, disease characteristics, and clinic site type. Results: 8128 men received BT (n=1117), BT+EBRT (n=313), EBRT alone (n=596), EBRT+androgen deprivation therapy (ADT, n=613), or RP (n=5489) for modified D’Amico low (n=3506), intermediate (n=2938) or high-risk (n=1684) disease. By t-tests, BT patients were younger than either EBRT or EBRT+ADT patients (both p<0.001), older than RP patients (p<0.001), and had lower risk disease than men in any of the four treatment groups (all Cochran-Mantel-Haenszel chi-square p<0.001). BT comprised 6.1% and 16.6% of all treatments in 1990-1998 and 1999-2011, respectively (Pearson p<0.01). The odds of BT use remained increased after adjusting for potential confounders (AOR 4.50, p<0.001). Increased BT use was seen only among low (AOR 5.06, p<0.001) and intermediate-risk patients (AOR 4.59, p<0.001). Among men with low or intermediate-risk disease, BT use increased compared with EBRT (AOR_LOW 10.00; AOR_INT 12.66, both p<0.001), EBRT+ADT (AOR_LOW 2.90, p=0.0037; AOR_INT 2.15, p=0.0041) and RP (AOR_LOW 4.76; AOR_INT5.10, both p<0.001). Conclusions: Despite national guidelines to the contrary, brachytherapy monotherapy for intermediate-risk prostate cancer increased over time relative to other treatments. Further studies are needed to identify factors that contribute to this evidence-practice gap.