5-(Nonyloxy)tryptamine (5-NOT) is a tryptamine derivative which acts as a selective agonist at the 5-HT<sub>1B</sub> receptor. Increasing the O-alkoxy chain length in this series gives generally increasing potency and selectivity for 5-HT<sub>1B</sub>, with highest activity found for the nonyloxy derivative, having a 5-HT<sub>1B</sub> binding affinity of 1.0 nM, and around 300-fold selectivity over the related 5-HT<sub>1A</sub> receptor.