A study was conducted at Meru/Usa forest plantation to determine quality, stocking and yield of Pinus patula and factors influencing them. The Meru/Usa forest plantation compartments were categorized into affected and non – affected by root disease and insect defoliators. Systematic sampling method was used to align transect and plots in the compartment. 198 sample plots of 0.04ha were laid and measurements taken for estimation of stem quality, stocking, basal area and volume. The data collected were analysed by micro-soft excel and SPSS computer programmes. The weighted means of combined roundness and straightness for the affected compartments were 51.9 ± 5.0%, 32.7 ± 5.9% and 15.5 ± 4.9% in grades of good, medium and bad; while for the non – affected compartments were 60.9 ± 6.9%, 21.7 ± 6.4% and 17.2 ± 3.2% in grades of good, medium and bad. In this study it was found that the overall weighted means in the affected and non-affected compartments were 56.4%, 27.2% and 16.4% in grades of good, medium and bad respectively. The computed parameters for the affected compartments were 569 ± 137 stems/ha, 17 ± 4 m 2 /ha and 129 ± 35 m 3 /ha; while for the non – affected compartments were 709 ±184 stems/ha, 23 ± 2 m 2 /ha and 153 ±37 m 3 /ha. The study concluded that the compartments were affected with improper implementation of silvicultural practices, presence destructive agencies (wild animals and humans), root disease (Armillaria mellea), drought, grazing and insect defoliators (Xanthisthisa tarspina). It was also found that Meru/Usa forest plantation has suitable trees that may fetch good price at the markets if silvicultural practices are implemented accordingly. It is recommended that the Meru/Usa forest project should carry out proper silvicultural practices and local communities should be educated, encouraged to adopt and practice agroforestry.