Certain phenylalkylamine derivatives have been considered to bind selectively at 5-HT2 serotonin receptors. It is now recognized that the most widely used derivatives, i.e., 1-(2,5-dimethoxy-4-X-phenyl)-2-aminopropanes where X = Me (DOM), Br (DOB), and I (DOI) (1-3, respectively) also bind at the more recently identified population of serotonin 5-HT1C receptors. The purpose of the present investigation was to determine whether simple phenylalkylamines bind selectively at one population of receptors over the other. An examination of 34 derivatives reveals (i) similar structure-affinity relationships and (ii) a significant correlation (r = greater than 0.9, n = 25) between 5-HT1C and 5-HT2 affinity. None of the compounds included in the present study displayed more than a 10-fold selectivity for one population of these receptors over the other; the results suggest that these compounds (including the widely used 5-HT2 agonists DOB and DOI) are 5-HT1C/5-HT2 agents.