The study of marine macroalgae collected in N Papua New Guinea in 1980, 1986, 1988 and 1990 resulted in 14 species (29 entities) of Caulerpa: C. biserrulata, C. cupressoides (5 ecads), c. elongata (2 ecads), C. filicoides var. andamanensis, C. lentillifera, C. manorensis, C. microphysa, C. opposita, C. racemosa (8 ecads), C. serrulata (3 ecads), C. sertularioides, C. taxifolia (2 ecads), C. verticillata, and C. webbiana ecad disticha. An identification key is added.