A long-term phenological study on primary tree species of a natural broadleaf forest was conducted in the Fushan experimental forest of northeastern Taiwan. The results of the 2-yrs investigation in 1993 and 1994 show that significant phenological phases occurred in various months, and are listed as follows: budding and leafing phase was from March to April; flower appearing phase in April; peak leafing phase from April to May; flowering phase from April to June; fruiting phase from July to October; and leaf falling phase for deciduous trees was from October to the following February.