Although four species of the genus Melocactus have been described in recent years from the Caribbean island of Curaçao, doubts have been expressed about the specific status of M. macracanthos, M. citrispinus, M. inclinatus and M. bozsingianus. Following research by the author on the adjacent island of Aruba, morphological study was made of 18 populations of the very variable plants of the genus on the island of Curaçao, using the same statistical techniques as in the previous work. In spite of the resemblance of some plants to the Aruban M. stramineus, the discovery of extremely small forms and the highly polymorphic nature of the plants, neither statistical analysis nor field observations could justify separation of morphs as distinct species. It is concluded that all melocacti in Curaçao are M. macracanthos. A study of detailed photographs of plants from several populations in Bonaire confirmed that they too belonged to that species. However, M. macracanthos in each of the islands exhibit distinctive characters in a high percentage of plants, especially in their spination and flower form, but variation is so great that no taxonomic distinction is justified.