Pyrimethamine has no unpleasant taste. Some babies were given crushed tablets with a drink of water to wash them down. No toxic effect was noted. Of the 47 who received weekly doses regularly, twelve revealed the gametocytes of P. falciparum in their blood films for two to six weeks. Blood films on all of the 134 regular people were negative at the end of the experiment. No clinical symptoms or relapse occurred during the 18 weeks of suppressive treatment in any of the treated people after the first 3 weeks, when all became free from asexual forms. This appears to be a very good drug for suppressive use if continued weekly. We get the same result with chloroquine but pyrimethamine is easier to administer.