Masters and Johnson
The Masters and Johnson research team, made up of William Masters and Virginia E. Johnson, pioneered research into the nature of human sexual response and the diagnosis and treatment of sexual disorders and dysfunctions from 1957 until the 1990s.
Their work began in the Department of Obstetrics and Gynecology at Washington University in St. Louis and was continued at the independent not-for-profit research institution they founded in St. Louis in 1964, originally called the Reproductive Biology Research Foundation and renamed the Masters & Johnson Institute in 1978.
In the initial phase of their studies, from 1957 until 1965, they recorded some of the first laboratory data on the anatomy and physiology of human sexual response based on direct observation of 382 women and 312 men in what they conservatively estimated to be "10,000 complete cycles of sexual response." Their findings, particularly on the nature of female sexual arousal (for example, describing the mechanisms of vaginal lubrication and debunking the earlier widely-held notion that vaginal lubrication originated from the cervix) and orgasm (showing that the physiology of orgasmic response was identical whether stimulation was clitoral or vaginal, and proving that some women were capable of being multiorgasmic), dispelled many long standing misconceptions.
They jointly wrote two classic texts in the field, Human Sexual Response and Human Sexual Inadequacy, published in 1966 and 1970 respectively. Both of these books were best-sellers and were translated into more than thirty languages.
They have been inducted into the St. Louis Walk of Fame.

# Research Work
Masters and Johnson met in 1957 when William Masters hired Virginia Johnson as a research assistant to undertake a comprehensive study of human sexuality. (Masters divorced his first wife to marry Johnson in 1969. They divorced three decades later, largely bringing their joint research to an end.) Previously, the study of human sexuality (sexology) had been a largely neglected area of study due to the restrictive social conventions of the time, with one notable exception.
Alfred Kinsey and his colleagues at Indiana University had previously published two volumes on sexual behavior in the human male and female in 1948 and 1953, respectively (known as the Kinsey Reports), both of which had been revolutionary and controversial in their time. Kinsey's work however, had mainly investigated the frequency with which certain behaviors occurred in the population and was based on personal interviews, not on laboratory observation. In contrast, Masters and Johnson set about to study the structure, psychology and physiology of sexual behaviour, through observing and measuring masturbation and sexual intercourse in the laboratory.
As well as recording some of the first physiological data from the human body and sex organs during sexual excitation, they also framed their findings and conclusions in language that espoused sex as a healthy and natural activity that could be enjoyed as a source of pleasure and intimacy.

# Four Stage Model of the Sexual Response
One of the most enduring and important aspects of their work has been the four stage model of sexual response, which they described as the human sexual response cycle. They defined the four stages of this cycle as:
- Excitement phase (initial arousal)
- Plateau phase (at full arousal, but not yet at orgasm)
- Orgasm
- Resolution phase (after orgasm)
This model shows no difference between Freud's purported "vaginal orgasm" and "clitoral orgasm": the physiologic response was identical, even if the stimulation was in a different place.
Masters and Johnson's findings also revealed that men undergo a refractory period following orgasm during which they are not able to ejaculate again, whereas there is no refractory period in women: this makes women capable of multiple orgasm. They also were the first to describe the phenomenon of the rhythmic contractions of orgasm in both sexes occurring initially in 0.8 second intervals and then gradually slowing in both speed and intensity.

# Sexual Response in the Aging Male and Female
Masters and Johnson were the first to conduct research on the sexual responsiveness of older adults, finding that given a state of reasonably good health and the availability of an interested and interesting partner, there was no absolute age at which sexual abilities disappeared. While they noted that there were specific changes to the patterns of male and female sexual responses with aging  for example, it takes older men longer to become aroused and they typically require more direct genital stimulation, and the speed and amount of vaginal lubrication tends to diminish with age as well  they noted that many older men and women are perfectly capable of excitement and orgasm well into their seventies and beyond, a finding that has been confirmed in population based epidemiological research on sexual function in the elderly.

# Sexual Dysfunction
Their research into the anatomy and physiology of sexual response was a springboard to developing a clinical approach to the treatment of sexual problems in a revolutionary manner. Prior to 1970, when they described their treatment program to the world for the first time, sexual dysfunctions such as premature ejaculation, impotence, vaginismus, and female frigidity had been generally treated by long-term (multi-year) psychotherapy or psychoanalysis with very low rates of success. Masters and Johnson revolutionized things by devising a form of rapid treatment (2 week) psychotherapy always involving a couple, rather than just an individual, working with a male-female therapist team that resulted in a success rate of more than 80%. This was strictly a talking therapy  couples in their sex therapy program were never observed in sexual activity.

# Treatment of Homosexual Behavior
From 1968 to 1977, the Masters and Johnson Institute ran a program to convert or revert homosexuals to heterosexuality.  This program reported a 71.6% success rate over a six-year treatment period. At the time of their earlier work, homosexuality was considered a psychological disorder by the American Psychiatric Association.

# Criticisms
Some sex researchers, Shere Hite in particular, have focused on understanding how individuals regard sexual experience and the meaning it holds for them. Hite has criticised Masters and Johnson's work for uncritically incorporating cultural attitudes on sexual behaviour into their research.
For example, Hite's work showed that 70% of women who do not have orgasms through intercourse are able to achieve orgasm easily by masturbation. She has criticised Masters and Johnson's argument that enough clitoral stimulation to achieve orgasm should be provided by thrusting during intercourse, and the inference that the failure of this is a sign of female "sexual dysfunction". While not denying that both Kinsey and Masters and Johnson have been a crucial step in sex research, she believes that people must understand the cultural and personal construction of sexual experience to make the research relevant to sexual behaviour outside the laboratory.

# Publications
- Masters, W.H. (1966). Human Sexual Response. Toronto; New York: Bantam Books. ISBN 0-553-20429-7. Unknown parameter |coauthors= ignored (help).mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
- Masters, W.H. (1970). Human Sexual Inadequacy. Toronto; New York: Bantam Books. ISBN 0-553-20699-0. Unknown parameter |coauthors= ignored (help)
- Masters, W.H. (1974). The Pleasure Bond. Toronto; New York: Bantam Books. ISBN 0-553-20915-9. Unknown parameter |coauthors= ignored (help)
- Masters, W.H. (1979). Homosexuality in Perspective. Toronto; New York: Bantam Books. ISBN 0-553-20809-8. Unknown parameter |coauthors= ignored (help)