Summary Growth hormone levels were analysed in three crown gall tumor cultures of Chaenactis douglasii (Asteraceae) in relation to polyacetylene accumulation and differentiation. All three tumor cultures, CD-5, CD-7 and CD-8, originated from transformation of stem cells by Agrobacterium tumefaciens strain A277, yet they displayed different morphologies. Only one of the lines, CD-5 showed accumulation of the polyacetylene thiarubrine and differentiated structures which correlated with xylogenesis. Analysis of auxin and cytokinin levels revealed major differences between the tumor cultures. Levels of isopentenyladenosine (IPA) in line CD-8 were approximately eight-fold higher than in the other two lines. CD-7, exhibited levels of bound indoleacetic acid (IAA) that were six-fold higher than in those of the other two, and trans-zeatin riboside levels that were only one-fifth of those of the other cultures. The transformed line CD-5 which produces thiarubrines showed approximately equimolecular amounts of auxins and cytokinins. Diffusible factors from this polyacetylene-producing tumor (CD-5) promoted growth of normal callus placed on top of it, but did not induce differentiation or polyacetylene production in the tissue. The different characteristics observed for the tumor lines suggest that the parental cell type which is transformed strongly affects the characteristics of the resulting tumor line.