To assess the safety and serum estradiol (E2) and total testosterone (T) concentrations in postmenopausal women treated with Pellet Hormonal Therapy (PHT) and Food and Drug Administration approved Hormonal Therapy (FHT). A total of 539 postmenopausal women were identified, including 384 on PHT and 155 on FHT. Data extracted from medical records include demographics, indication for hormone therapy, treatment duration, side effects, serum E2 and T levels, and frequency of laboratory follow-up. The incidence of overall side effects was significantly higher in PHT compared with FHT (221 [57.6%] vs 23 [14.8%], P < 0.00001, odds ratio [95% CI] =8.0[4.5-14.2]). When examining women with an intact uterus prior to hormone therapy initiation, 55.3% (136/246) on PHT vs 15.2% (12/79) on FHT had at least one episode of abnormal uterine bleeding (P < 0.0001, odds ratio [95% CI] = 7.9[3.6-17.0]). Furthermore, a significantly higher proportion of women on PHT (20.3% [50/246]), compared with 6.3% (5/79) on FHT, had a hysterectomy (P = 0.036, odds ratio [95% CI] = 3.2[1.1-9.3]). Both mean (SD, Min-Max) peak E2 (pg/mL) and peak T (ng/dL) are significantly higher in the PHT group than those in the FHT group (E2: 237.70 [168.55, 10-1,111] vs 93.45 [130.77, 5.5-465.8], T: 194.04 [84.94, 4.3-599] vs 15.59 [19.52, 0.2-70], P < 0.00001). Of those on PHT, four women had E2 level > 1,000 pg/mL and nine women with T level > 400 ng/dL. Women on PHT had a significantly higher incidence of side effects than FHT as well as a significantly higher supraphysiological level of peak E2 and T during the treatment.