Gender dysphoria is a medical condition characterized by a disconnection between someone's assigned and perceived genders. Individuals with gender dysphoria usually identify themselves as transgendered or transsexual, depending on their ideological feelings about sex and gender. Some transgendered individuals also disagree with the categorization of gender dysphoria as a medical condition, as part of a larger exploration of gender identity and what “normal” gender is. It is also important to differentiate a transvestite from someone with gender dysphoria; medically, a transvestite is someone who wears clothing belonging to the opposite gender, but is both happy and secure with his or her gender identity.

People of all ages can experience gender dysphoria, although most patients experience a sense of disconnection from a very young age. A little boy who longs to be a little girl throughout childhood may not seek treatment until he is much older, but the underlying feelings are still there. Adolescence is also a common time period for the emergence of symptoms, while, more rarely, some adults only start to question their gender when they are much older. The acceptance of gender dysphoria as a condition requiring compassionate treatment, rather than an abnormality, began in the mid twentieth century, but was not widespread until the 1980s.

Individuals with gender dysphoria who seek treatment usually start by seeing a psychologist to discuss their feelings. Working together with a psychologist, the patient decides how serious the problem is, and whether steps should be taken to bring his or her physical gender into alignment with the perceived gender. In most nations, a patient must be seeing a psychologist about the problem for a minimum of one year before taking the next step in treatment, to ensure that the patient truly has gender dysphoria, rather than a passing phase. In most cases, the next step begins with living life in the other gender part time; a man transitioning to a woman, for example, may start going to the store in dresses, and will also begin discussing the problem with the people in her life.

There are a number of treatments that can be used to transition between genders. The first is hormone treatment, which will physically alter the body. After a set period of hormone treatment, the patient may consider surgery to modify genitalia and the chest region. During hormone treatment, the patient usually begins to transition full time, dressing and behaving in ways which match his or her perceived gender, and sometimes taking voice training and other lessons to learn how to walk, talk, and “pass” as the new gender. At the end of the treatment, the transgendered individual will have fully transitioned into a new gender.