About 60 species, nearly worldwide, most diverse in the New World tropics.

Traditionally, Melochia has been treated in the segregate family Sterculiaceae, a mostly tropical group of some 65 genera and more than 1000 species, these mostly shrubs or trees. However, molecular studies have shown that the genera group into two main lineages, one of which appears more closely related to one of the two major groups of former Tiliaceae and the other of which is only distantly related within the Malvaceae in the broad sense and closer to the other portion of the former Tiliaceae (Whitlock et al., 2001).

It should be noted that the flowers of some species of Melochia do not possess an epicalyx of closely subtending bracts and such species cannot be correctly identified to genus in the key above. Also, members of Melochia tend to produce long-styled and short-styled flowers (heterostyly). The staminal tube can be relatively short in long-styled flowers.