Wood samples of Gmelina arborea were collected from four different localities (sites) in Nigeria. The proportion of vessels was determined by a modification of Ladell's (1959) randomized dot technJqff~. The site and plot effects on vessel proportion were not significant. The tree effect was very highly significant with a variance component of up to 25.4 per cent. The tree mean values of vessel proportion ranged from 9 to 21.3 per cent. There was no dose correlation between tree mean values of vessel proportion and tree growth parameters (tree height, diameter at breast height and crown diameter). The effect of stem height was not significant. The effects of radii (the variation around the stem's circumference) and age were very highly sit, nificant with variance components of up to 21 and 11.7 per cent respectively. The differences in the values of vessel proportion for earlywood and latewood were very highly significant; the variance component was 22.9 per cent. Earlywood had a lower proportion of vessels than latewood (12 and 16 per cent respectively). Vessel proportion was not correlated with ring width. The effects of factor interactions were not practically important.