We measured the values for biomass and mean annual biomass increment (MAI) of planted forests in two parts of the Tropical Dry climatic zone (mean annual precipitation [MAP] < 1,000 mm) and in one site adjacent to one of the two parts and outside the Tropical Dry climatic zone to provide a comparison value for wet forests in the same region. MAI values of four planted forests averaged 2.60 (± 1.61 SD) Mg ha^-1 y^-1 at a MAP of 637 mm in the central dry zone of Myanmar. The MAI of exotic fast-growing tree species (Eucalyptus camaldulensis Dehn.) did not differ significantly from those of three native non-fast-growing tree species in the central dry zone of Myanmar. MAI values appeared to be lower on land with a high gravel content in the soil or with a higher degree of erosion. In the eastern part of Sumba Island in Indonesia, MAI of planted Tectona grandis L. forest equaled 3.76 Mg ha^-1 y^-1 at a MAP of 500 mm and 4.49 Mg ha^-1 y^-1 at a MAP of 1,500 mm. A Leucaena leucocephala de Wit stand produced a higher MAI (9.62 Mg ha^-1 y^-1) at a MAP of 500 mm. The MAI values for fast-growing tree species that we measured or collected in the Tropical Dry climatic zone were less than 20% of those recorded in the Tropical Moist and Tropical Wet climatic zones and about one-third the value for forests of non-fast-growing tree species. Accordingly, fast-growing tree species may not be capable of achieving their fast growth rates under the Tropical Dry climate. This information will be useful in developing land-use programs based on plantation forestry in dry forest areas.