The monotypic genera Absolmsia Kuntze, Madangia P. I. Forst., Liddle & I. M. Liddle, and Micholitzia N. E. Br. (Apocynaceae, Marsdenieae) are, according to molecular phylogenetic results, nested within the genus Hoya R. Br. Together with Dischidia R. Br., these genera are considered to comprise a well-supported clade within the tribe Marsdenieae. Flower morphology of Absolmsia, Madangia, and Micholitzia is examined by SEM and light microscopy and compared to that of the related H. caudata Hook. f., H. curtisii King & Gamble, H. hypolasia Schltr., H. lacunosa Blume, H. patella Schltr., H. retusa Dalzell, and H. venusta Schltr. We discuss the morphological evidence that supports the reduction of these genera into Hoya. Among characters supporting such a position is the presence of a pellucid margin on the pollinia of Absolmsia, Madangia, Micholitzia, and Hoya that is absent on the pollinia of Dischidia. Absolmsia and Madangia have a staminal corona with outer and inner lobes, similar to that of Hoya. While the outer corona processes of Absolmsia and Micholitzia are free and revolute, as in most species of Hoya, those of Madangia are laterally fused forming a continuous skirt resembling the corona of certain species of Hoya. The flowers of Micholitzia are superficially similar to those of Dischidia in its urceolate corolla, but the staminal corona with revolute outer processes decidedly links Micholitzia to Hoya. The new combination H. inflata (P. I. Forst., Liddle & I. M. Liddle) L. Wanntorp & P. I. Forst. is proposed. For Micholitzia obcordata N. E. Br., the name H. yuennanensis Hand.-Mazz. has nomenclatural priority and should therefore be used when including M. obcordata in Hoya.