An overview is presented of important issues having to do with relationships between humor and biology, including those having to do with the genetic origin of the sense of humor, physiology of mirthful response to humor, impacts on health of humor physiology. Discussion isprovidedon theoretical implications derived from the complex relationship between humor and biology.During the earlier half of this Century, it was widely believed that a sense of humor is a learned component of human life. It was considered that it would not be too much of a shock to discover groups, even entire cultures where humor had never been developed and where people are entirely devoid of a sense of humor. Such a group has never been discovered.Occasionally, an allegedly humorless person is pictured in vivid color on the front page of checkstand tabloids, with dramatic headlines -"lost bis way to laughter," "sees nothing funny in life." These poor souls are invariably found to be suffering with but a temporary dislocation or suppression of their natural capacity for humor and mirth and laughter.No person or group of persons has been found to be without a sense of humor, except on a temporary basis because of some dire personal or national tragedy which for the time being has caused an eclipse of humor. This demonstrated ubiquity of humor is compatible with the contemporary view of how deeply humor is bred into human existence. Rather than being regarded äs learned, äs it was previously, humor is now considered to be a genetic, biologic characteristic of the human race.As a result of a variety of studies -most prominently of infant and