The effects of tryptamine on the induction of a conditioned taste aversion (CTA) to a novel saccharin solution were examined. In a single bottle-repeated injection paradigm, tryptamine (40, 60 and 80 mg/kg, IP) induced a significant CTA. This effect was relatively weak, with only the highest dose tested inducing a progressive decline in saccharin intake across trials. The weak action of tryptamine (40 and 60 mg/kg) was confirmed in a more sensitive CTA paradigm which measured the relative preference for saccharin and water. Results of this experiment also showed that prolonging the duration of action of tryptamine failed to enhance the formation of a CTA. This finding extends previous reports that prolonging the duration of action of a compound does not increase potency in the CTA paradigm, and thus casts doubt on the generality of the duration of action hypothesis.