Small tree-like or shrubby, usually much branched. Stems elongated, erect or ascending. Segments of the branches upright, fluted or angled, sometimes with annual constrictions, strongly ribbed, ribs 3 – 14 on each segment. Areoles of stem and branches spiny, spines many, acicular. Leaves absent. Flowers infundibuliform, nocturnal, usually white, flowering areole more or less spineless, lateral or subterminal (apical), actinomorphic, conspicuous. Pericarpel and tube usually naked or nearly so below and with scattered small scales above. Perianth early deciduous. Perianth tube nearly cylindric, ± expanded apically, limb broad or moderately so, outer tepals sepaloid, obtuse, inner tepals petaloid, acute, usually bright white. Stamens many, not exserted, differing in size. Style persistent and recurved. Stigma linear, numerous. Ovary scaly. Fruit fleshy, globose, ovoid or oblong, spineless, usually red, rarely yellow, dehiscing along one side, pulp white, rarely pink or red. Seeds numerous, black.

A genus of about 35 species, mainly distributed in South America and West Indies. One species is cultivated in Pakistan.