A new monotypic genus from Madagascar, Voanioala gerardii, has at least 2n = 596 chromosomes, the highest number known in the monocotyledons and exceeded perhaps by only a single known dicotyledon count, namely Sedum suaveolens (2n = ca. 640). Two seedlings had 4C DNA amounts of 122.0 ± 5.6 and 117.4 ± 8.0 pg, respectively. Chromosome lagging was common in mitotic cells and probably results in somatic variation in chromosome number, but somatic polyploidy derived from endoreduplication was not detected.Key words: Voanioala, palm, new genus, high chromosome number, polyploidy, C-value.