Résumé : Plectranthus inselbergi B. J. Pollard & A. J. Paton, is described from Equatorial Guinea and Gabon, illustrated and its ecology and taxonomic relationships are discussed. Three new combinations and a new name in Plectranthus L'Hér. are provided for related species formerly placed in Solenostemon Thonn., and conservation assessments are made for all five species. Some observations on P. decumbens Hook. f. are also made. © The Board of Trustees of the Royal Botanic Gardens, 2006.