The summit zone of Mt Kinabalu (4101 m) largely comprises exposed rock, but nevertheless includes in its flora plants with various and geographically distant affinities. The vegetation of the zone has not hitherto been adequately described. Eighty-three plots with 98 vascular plant species were studied. Vegetation types recognized are upper mountain forest (3260 to 3550 m), summit scrub (3720 to 3950 m), sayat-sayat scrub (3300 to 3800 m), summit heath (3850 to 4020m), three depauperate crevice communities (together 3330 to 4040m), seepage fens (3320 to 3590 m) and sandy depressions (3500 to 4040 m). All except upper mountain forest and the crevice communities are very local in distribution, and none are anthropogenic. Ecological controls are suggested. Disturbed vegetation along the summit path is also described, and alien species are listed. Comparison is made between the vegetation of Mt Kinabalu and; of mountains in New Guinea.