Tropical rainforests contain many "lesser known species" that have not achieved widespread acceptance in international timber markets. This paper provides a quantitative analysis of the effects on tropical log demand of two economic factors: relative prices and technical change. A multi-output cost function framework is developed to analyze tropical log demand as derived from the production of plywood and sawnwood. Data analyzed are Japanese imports of dipterocarp and nondipterocarp logs (proxies for well- and lesser known species, respectively) from the South Seas during 1970-87. The econometric results indicate that the composition (dipterocarp vs. nondipterocarp) of tropical log imports was not significantly influenced by either relative prices or technical change during the period analyzed. For. Sci. 36(3):657-664.