Corynebacterium fascians causes a fasciation disease in a number of dicotyledons and this disease appears to be caused by compounds with cytokinin activity elaborated by the infecting bacteria. Extractions of C. fascians in late logarithmic phase under conditions where the pH never falls below 7.0 yield about 2 μg/l of N (6)-(Δ(2), a potent cytokinin. If a mild acidification step is included in the extraction procedure the yield increases to about 12 μg/l. This is due to release of N (6)-(Δ(2)-isopentenyl)adenine from C. fascians tRNA during the extraction procedure. In terms of total cytokinin activity present in C. fascians cultures, N (6)-(Δ(2)-isopentenyl)adenine appears to be a minor component.