Selected substituted piperazine compounds of Formula I ##STR00001## are effective for prophylaxis and treatment of diseases, such as obesity and the like. The invention encompasses novel compounds, analogs, prodrugs and pharmaceutically acceptable salts thereof, pharmaceutical compositions and methods for prophylaxis and treatment of diseases and other maladies or conditions involving activation of the melanocortin receptor. The subject invention also relates to processes for making such compounds as well as to intermediates useful in such processes.