Structural studies on the six alkaloids isolated from Tylophora crebrijlora (N. 0. Asclepiadaceae) are described here. Spectral data indicate that five of these alkaloids (A-E) possess the dibenzo[f,h]pyrrolo[l,2b]isoquinoline skeleton known to be present in tylocrebrine. They differ in the number, nature, and distribution of the oxygen-bearing substituents and in the presence or absence of a benzylic-type hydroxyl. An oxygen substitution pattern of 3, 4, 6, and 7 is suggested for Alkaloids A, B, and C and that of 2, 3,4, 6, and 7 for Alkaloids D and E. Alkaloid F is shown to be a seco analog of tylocrebrine with a 1,2diphenyl cis stilbene skeleton.