The two species of Aidia Lour. (Rubiaceae, Gardenieae) newly described here bring this genus to three species in Tanzania and Kenya. Aidia abeidii S. E. Dawson & Gereau, from evergreen coastal forests of eastern Tanzania and Kenya, corresponds to an unnamed species mentioned in the Rubiaceae treatment for the Flora of Tropical East Africa. Aidia crassifolia S. E. Dawson & Gereau, from evergreen forests of northeastern and east-central Tanzania, is a larger tree or shrub with much larger inflorescences than the other two species of Aidia in tropical East Africa. The new species of Polysphaeria Hook. f. (Rubiaceae, Octotropideae), P. ntemii S. E. Dawson & Gereau, from evergreen forests of the East Usambara lowlands in Tanzania, corresponds to Polysphaeria sp. B of the Flora of Tropical East Africa.