The behavioral data reviewed herein must be viewed with caution. Although there are reports that adhere to rigorous methodology, these are the exception. Most reports do not adequately describe either the methodology used or their sample. Subjects are often of mixed endocrine diagnoses, and sometimes the results are of both boys and girls. All of these pitfalls make interpretation of results difficult and limiting. With this in mind, the following conclusions are offered. The majority of behavioral data on precocious puberty comes from studies of IPP in girls. Cognitively, IPP has been associated with average to high-average intelligence. Purportedly, the finding of lower visual-spatial skills than verbal skills in early maturing boys and girls has received equivocal support by cognitive studies of IPP individuals. Similarly, clear differences in hemispheric lateralization have not been demonstrated. Aside from increased somatic complaints during the nonmenstrual phases of their menstrual cycle, girls with IPP show a spectrum of behavior adjustments. Major psychopathology is rare. Clearly, their early development makes them look older than their actual age, which probably alters the expectations others have for them. Psychosexually, however, IPP girls develop in concert with their chronologic age and social experience, rather than their early biologic maturation. However, recent reports suggest a modest influence of hormones. In summary, these studies support an interactionist theory of human psychosexual development. Research data on IPP girls suggest that they do not significantly differ from girls who are early maturers but within the normal range. Research on these girls indicates that most negotiate their puberty without severe problems. There has been less research on IPP boys because it occurs so rarely. Most of what is understood about precocious puberty in boys comes from boys with precocious puberty secondary to poorly controlled CAH. Behavioral data on individuals with delayed puberty come almost exclusively from boys. Although CD appears to be the most frequently diagnosed form of delayed puberty and does not reflect a known pathologic process, men with CD as well as those with organic disorders appear to be at risk for psychosocial and psychosexual difficulties. These difficulties are not severe forms of psychopathology. Rather, they probably represent problems negotiating the expected adolescent lessons of psychosocial development with a physique that places them at a disadvantage. They clearly look younger than their actual chronologic age. Cognitively, as with the children with precocious puberty, there is no evidence of intellectual impairment associated with delayed puberty.(ABSTRACT TRUNCATED AT 400 WORDS)