An account is given of the results obtained with a number of p‐aminopbenoxyalkanes which were examined for activity against Schistosoma mansoni in mice and for the presence of retinotoxicity in cats. The first compound to be found active, 1: 5‐di(p‐aminophenoxy)‐pentane dihydrochloride (M & B 968A), was modified in a variety of ways in an attempt to increase its activity and to eliminate its ocular effects. It was found that a p‐aminophenoxyalkyl group was common to all the active compounds, but that the rest of the molecule could be any of several different groups, including alkoxy, phenoxy, and phenyl groups, without diminishing the activity. Although at least one p‐aminophenoxyalkyl group was essential for schistosomicidal activity, ocular toxicity was also shown by a p‐aminophenylalkyl derivative in which the ether linkage was absent.