Samples collected around Madagascar and La Réunion, which included seven species of the genus Heterocarpus, led to the re-examination of all the Heterocarpus (nine species) reported previously from the region. A new species, H. calmani, which has been confounded until now with H. woodmasoni Alcock, 1901, is described. The occurrence of H. lepidus de Man, 1917, of which the specimens collected in the region had been identified wrongly as H. tricarinatus Alcock and Anderson, 1894, is proved. The re-examination of the type of H. unicarinatus Borradaile, 1915, only known specimen of this species, permits the completion of its description, but makes one wonder if this species really belongs to the genus Heterocarpus. Comparisons between specimens from Madagascar and La Réunion and specimens from the West-Pacific and from the Atlantic permit the consideration of variations associated with geographical areas and depth of sampling for H. dorsalis Bate, 1888, H. ensifer A. Milne Edwards, 1881, H. laevigatus Bate, 1888, H. lepidus de Man, 1917, and H. sibogae de Man, 1917. These comparisons also allow better definition of the features separating H. lepidus from H. gibbosus Bate, 1888, and H. tricarinatus. A careful examination of the "ensifer" complex permits the description of two new species, H. amacula and H. hayashii, and the elevation to specific rank of H. parvispina, considered, until now, to be a subspecies of H. ensifer. On the other hand, H. tricarinatus is split into two subspecies, H. tricarinatus tricarinatus, found in the Indian Ocean, and H. tricarinatus angustus subsp. nov., found in the West-Pacific. A key is offered for the identification of the 25 recognised species and subspecies of the genus. Moreover, attention is drawn to the interest often presented by the coloration in the species of this genus.