A new steroidal alkaloid, soladunalinidine (1), was obtained by counter-current distribution of the crude aglycone extract from Solanum dutinum Gaud. collected near Weipa in Queensland in November 1974. It has the molecular formula C27H44N2O, and was obtained as a colourless non-crystalline solid with m.p. 145-153°C, [α]D^35 +1.30° (c, 0.46 in CHCl3). Infrared spectrum showed strong absorption at 3420 cm^-1 (NH), 1H NMR spectrum was similar to that of tomatidine (2), and mass spectrum indicated a spirosolane structure with molecular ion m/e 414. Formation of picrate, salicylidene derivative, and p-hydroxybenzylidene derivative confirmed the presence of a primary amino group. Acetylation gave a diacetyl derivative. 13C NMR analysis showed soladunalinidine has the same structure as tomatidine except for a 3-amino group substituting the 3-hydroxyl group in ring A, supported by comparison with 3α-amino-5α-cholestane and circular dichroism data of the salicylidene derivative. Structure was verified by chemical correlation: nitrosation and rearrangement of diacetylsoladunalinidine yielded O,N-diacetyltomatidine identical to an authentic sample. Soladunalinidine is the first naturally occurring 3-aminospirosolane isolated from a Solanum species.