This work presents a taxonomic study on the Late Maastrichtian radiolarian fauna from ODP Leg 165, Hole 999B, Colombian Basin. The studied fauna is composed by 24 species, being the family Archaeodictyomitridae Pessagno, 1976 the most abundant and diverse. Original opaline skeletons are replaced by calcium carbonate and precise identifications are possible only for those specimens with sturdy skeletons, what strongly suggests a preservational bias. The studied radiolarian fauna was attributed to the Amphipyndax tylotus zone, due to the occurrence of that species. Besides, the fauna described herein presents a low to intermediate latitude paleobiogeographic affinity and falls within the designation of a typical lower bathyal to abyssal one. Finally, the data presented herein are compared to those reported from the closely related ODP Hole 1001B.