plant density is one of the cropping practices that has the largest impact on individual plant growth. this work was conducted to evaluate the response of white oat (avena sativa) cultivars with contrasting tillering patterns to variations in plant density. two field experiments were carried out in lages, sc, brazil, during the 1998 and 1999 growing seasons. a split plot experimental design was used. four oat cultivars were tested in the main plots: ufrgs 14, ufrgs 18, upf 16 and upf 17 using five plant densities split plots: 50, 185, 320, 455 and 550 plants m-2. five plant samples were taken 25, 34, 48, 58 and 70 days after plant emergence to assess the treatment effects on dry matter partition between main stem and tillers. ufrgs 18 promoted dry matter allocation to tillers whereas upf 17 directed dry mass mostly to the main stem. differences in dry mass allocation between the main stem and tillers had no impact on grain yield, upf 16 presenting the highest values for both growing seasons. the lack of interaction between population density and cultivar and the small effect of plant population on grain yield indicates that the oat tillering ability is not fundamental to define its grain yield.