While humor can backfire or, worse, mask dark, underlying prejudices, research reveals positive and promising connections between humor and creativity, efficiency, and mental health. Although there remains considerable room for disagreement on the essential qualities of humor, several researchers after reviewing the literature appear to have focused on a core quality: incongruity, as experienced cognitively and affectively. Stimulus characteristics familiar to most people are items such as cartoons, jokes, and certain behaviors that contain unexpected, illogical, exaggerated, or out of context elements. These incongruities are often at the core of humor and are best appreciated by the more cognitively complex individual. Three theories (emphasizing the cognitive foundations of humor) have achieved prominence: incongruity theory, relief theory, and superiority theory. The various functions of humor are: psychological, sociological, educational (communication value), and physiological. Used effectively, the following guidelines may enhance learning in the classroom: (1) embrace humor and believe that it works; (2) know your audience; (3) be willing to laugh at yourself; (4) do not waste valuable class time on humor that is aimless and without purpose; (5) encourage a climate of reciprocal humor: (6) use visual examples or presentations to help maintain student attention; (7) consider asking students to use humor in answering test questions; and (8) begin class with a joke and use humorous stories and anecdotes. Used effectively and appropriately, humor can increase the satisfaction and productivity of students and teachers. (Sixty-four notes are included.) (RS)