The antirnalarial activity of sixteen ent-kaurenes was assayed on male albino mice infected with Plasmodium berghei. Ent-kaur-16-en-19-oic acid (kaurenic acid), l5iα-hydroxy- ent-kaur-16-en-19-oic acid, 15α-acetoxy- ent-kaur-16-en-19-oic acid, and ent-kaur-9(11)16-en-19-oic acid, natural kaurenes