The genus Epilobium (Onagraceae) comprises about 200 species, but is best represented at relatively high latitudes. Only eight species of the genus occur in Malesia, but they are interesting phytogeographically and shed considerable light on the overall patterns of differentiation in the genus. Further, it is of particular interest to review this assemblage of species for the following reasons. The only comprehensive treatment of the genus Epilobium is that of Carl Haussknecht, who in 1884 published his Monographie der Gattung Epilobium. At the time Haussknecht wrote, not a single collection of the genus had been made in Malesia, although three of the eight species in the area had been described from material obtained elsewhere. There has been no attempt to review the species of Epilobium found in Malesia as a whole or in any of its subdivisions, although of course new species have been described from the area from time to time. Of the eight species of Epilobium found in Malesia, four are endemic to the area. All of these endemic species are found in New Guinea, but one (E. prostratum) also occurs in Celebes and Central Ceram. As might be expected, this is the species which occurs at the lowest elevations in New Guinea, and is the least restricted to alpine grasslands, occurring also in moist, disturbed areas that are moderately shaded, as on roadbanks and along streams. This group of four New Guinea species shows evident affinities with some of those found in the Australasian region. Thus there are four groups of the genus currently recognized as occurring in New Zealand and Australia, all essentially endemic to the Australasian area [Allan, Fl. N. Zealand 1 (1961) 254—281]. Three of the New Guinea species — E. detznerianum, E. hooglandii, and E. prostratum — belong to the group Microphyllae, the fourth — E. keysseri — to the group Similes. Another species of Australia and New Zealand, E. cinereum, ranges northward to east Java and the Lesser Sunda Islands (and is also shown in this paper to be introduced in the Hawaiian Islands of Maui and Hawaii).