To analytically characterize the doses of estradiol and progesterone found in compounded combined forms of oral capsule and transdermal cream formulations, and determine the consistency of the hormone formulations within a batch.Prescriptions for combined estradiol/progesterone capsules (0.5 and 100 mg, respectively) and creams (0.5 and 100 mg/g, respectively) were sent to 15 custom-compounding pharmacies. Estradiol and progesterone levels were measured by radioimmunoassays. Hormone levels were measured in 2 capsules and 2 creams from each pharmacy; 10 capsules from 3 pharmacies; and top/middle/bottom layer of cream containers to assess consistency. The magnitude and sources of variation for the measurements were examined by analysis of variance models.Thirteen pharmacies filled the prescriptions. Measured estradiol levels were 0.365 to 0.551 mg for capsules and 0.433 to 0.55 mg/g for creams, and progesterone levels were 90.8 to 135 mg for capsules and 93 to 118 mg/g for creams. Greater variations in estradiol levels were observed between pharmacies for estradiol in capsules than in creams; however, measured estradiol levels within pharmacies were more consistent in the capsules than the creams. Similar results were obtained for progesterone levels.The variations in estradiol and progesterone levels observed in compounded hormone therapy formulations justify concerns regarding risks as a result of variability, which have been outlined by The North American Menopause Society, the American College of Obstetricians and Gynecologists, and the US Food and Drug Administration (FDA) in their statements regarding compounded hormone use. These data support the need for an US FDA-approved bioidentical hormone therapy.This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0 : Video Summary: Supplemental Digital Content 1, http://links.lww.com/MENO/A425.This is an open access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. http://creativecommons.org/licenses/by-nc-nd/4.0.