Regarding professional competence, the standards require that a person assessing or treating paraphiliac or sex offending problems have clinical training and experience in the diagnosis and treatment of a range of psychiatric and psychological conditions and also have specialized training and experience in the assessment and treatment of paraphiliac and sex offender problems. Treatment providers must be competent in making a differential diagnosis. Regarding antecedents to sex offender treatment, the standards require that the patient meet diagnostic criteria for paraphilic sexual disorder and that prospective patients receive a thorough physical examination, including the measurement of sexual hormones. Prospective patients should also receive a psychiatric examination that would rule out other psychiatric disorders. If medication is required, the patient must be given information regarding the benefits and potential side effects or disadvantages of biomedical treatment. Patients should give informed written consent for biomedical procedures to be performed. Seventeen principles of standards of care are provided. 2 references and appended standards for use of the penile plethysmograph