In Masters and Johnson's studies from 1957 until 1965, they recorded laboratory data on the anatomy and physiology of human sexual response based on direct observation of 382 women and 312 men aged between 18 and 89 in having sex or masturbating.
Johnson, who died in 2013 at 88, is sometimes described as a sexologist or psychologist. In reality, she had been studying for a sociology degree when Masters took her on, but the demands of their work prevented her from completing her degree.
One of the most important contributions of their work was identifying the four stages of sexual response: 1. Excitement phase (initial arousal) 2. Plateau phase (at full arousal, but not yet at orgasm) 3. Orgasm 4. Resolution phase (after orgasm) They showed that these occurred in both sexes.
William H. Masters and Virginia Johnson's work began in the Department of Obstetrics and Gynecology at Washington University in St. Louis and continued at the not-for-profit research institution they founded in St. Louis in 1964. It was called the "Reproductive Biology Research Foundation" and renamed the "Masters & Johnson Institute" in 1978.
They debunked Sigmund Freud's assertions about the difference between "vaginal orgasm" and "clitoral orgasm" (which he deemed "immature", proper only for pubescent girls). In their findings, the physiological response was identical.
In the series, Virginia has been married and divorced twice before meeting Dr. Masters. In reality, she may have been married three times, although there is conflicting information on whether one of the marriages was legal.
Allison Janney had a clause in her contract for this show stipulating that she would not do any full nudity, but after a few episodes playing Margaret she felt confident enough and understood that it might be dramatically necessary to do so, and she eventually did it in the powerful scene in which she shows her breasts to Barton and realized he's not even looking at them.
Paul Bettany had originally agreed to star as Dr. William H. Masters, but withdrew and was replaced by Michael Sheen. Interestingly, Bettany is British and Sheen is Welsh, while the real-life Masters was born and raised in the U.S.
Annaleigh Ashford was visibly pregnant during season 4, so her body was modified with CGI or hidden behind objects as much as possible. She ended up missing the last three episodes of the season when eventually gave birth.
Exteriors of the Washington University Medical Center were filmed outside the Irving Thalberg Building at Sony Pictures (formerly MGM) in Culver City. This building had previously been used for exteriors of Blair General Hospital in the "Dr. Kildare" movies and TV series.
The trivia items below may give away important plot points.
In real life, Masters met Virginia Johnson in 1957 when he engaged her to assist him in the research into human sexuality he had begun a few years earlier. Masters divorced his first wife, Elizabeth Ellis Masters, to marry Johnson in 1971. They were divorced in 1993. The following year, Masters retired and closed the institute. He died in 2001. Johnson died in 2013.
The decision to make Virginia a mother for the third time and the disclaimer after each episode from season 3 on indicating that Tessa, Henry or Johnny are fictitious characters were done to avoid legal action from the real life children and grandchildren of William Masters and Virginia Johnson.