The bark and leaves of the rain-forest tree Kopsia longiflora Merrill (Apocynaceae) contain four new alkaloids ; kopsinine, C21H26O2N2, (0.2 per cent.), kopsilongine, C24H30O6N2 (0.06 per cent.), and kopsamine, C25H30O7N2 (0.02 per cent.) occurring in the bark ; and kopsilongine (0.07 per cent.), kopsamine (0.3 per cent.), and kopsiflorine, C23H28O5N2, (0.04 per cent.) in the leaves. The bark also contains β-amyrin (0.35 per cent.) while the leaves afford a mixture of paraffin hydrocarbons, mainly n-hentri- acontane, β-sitosterol, a sterol, C29H50O2, and a triterpene alcohol acetate, C32H52O2. Kopsamine, kopsilongine, and kopsiflorine each contain two methoxyl groups, while kopsinine contains only one ; kopsamine and kopsilongine also contain methylene-dioxy-groups. No reactive carbonyl groups were detected. The alkaloids all titrated as monoacid bases and formed monomethiodides: while the ultraviolet spectra recorded in acid and neutral media show that the basic (tertiary) nitrogen atom does not contribute to the chromophoric system.