Two field experiments on weed control in soybeans were carried out at BIOTROP, Bogor, Indonesia 
from February to June, 1989. The critical period for weed control was found to be between 20 - 40 days after 
planting of soybean (c. v. Wilis) grown at a planting distance of 40 x 10 cm. It did not coincide with the fastest 
growth  in  terms of  trifoliate  leaf number. Further studies were suggested  to understand the physiological 
growth of soybean related to weed control. 
Pendimethalin at 660- 1320 g a.e./ha applied one day after sowing did not cause any phytotoxic effect to 
soybean and had good weed control performance.