Ring width variation was carried out on six straight trees of Pinus merkusii collected from Anjaw District of Arunachal Pradesh. The main aim of the present study was to evolve a sampling procedure for comparison of ring width variation amongst trees. Despite of straight trees, some eccentric cross- sectional discs with wide rings on lower side were observed. There was a statistically significant variation in ring width around the circumference at breast height. A non-significant variation between the mean of two opposite directions versus mean of eight cardinal directions suggested that any two opposite directions can be selected for comparison of ring width amongst Merkus pine. The radial variation in ring width at breast height and successive heights showed maximum ring width near the pith with irregular decrease towards the bark. There was a negative and highly significant correlation between ring width and age (r = -0.689**). Ring number 15 can be considered as a boundary between juvenile wood (Rings1-15) and mature wood (Rings 16-bark). There was irregular increase and decrease in ring width variation in selected rings from base to top in both vertical and oblique sequences in all trees.