<p><i>Rhododendron</i> species namely <i>R. anthopogon, R. camelliiflorum, R. campylocarpum, R. cinnabarinum, R. dalhousiae, R. falconeri, R. fulgens, R. grande, R. lanatum, R. thomsonii</i> and <i>R. wightii</i> collected from West Kameng and Tawang districts, Arunachal Pradesh were taken to study the detailed anatomical features of selected shrub and tree species of Rhododendron of Arunachal Pradesh, India with reference to their ecological and phylogenetic implications. For each species, 5 wood samples were randomly collected at breast-height for trees and main stem internodes above base for shrubs. Wood anatomical characteristics of the selected species were homogeneous. In all the selected <i>Rhododendron</i> species, growth rings were distinct, and wood diffuse-porous except semi-ring porous wood in <i>R. campylocarpum.</i> Vessels were solitary and angular in outline, uniformly distributed, tube-shaped with tails, helical thickenings throughout vessel body except vessel tail of <i>R. anthopogon</i> and <i>R. lanatum</i>, tyloses absent except in <i>R. camelliiflorum</i> and <i>R. thomsonii</i>; scalariform perforation plates, inter-vessel pits opposite, minute-small in size and vessel-ray pits with distinct borders similar to inter-vessel pits. Fibres were small, thin-walled, bordered pits, occasionally septate and parenchyma paratracheal scanty, 2–5 cells/strand with simple pits. Rays were uniseriate, biseriate and multiseriate. Multiseriate rays had uniseriate wings on one/both ends. Homocellular rays were made up of upright/square cells, heterocellular rays were consisting of body ray cells procumbent and upright and/or square marginal cells, and disjunctive ray parenchyma cells. Fibre percentage was highest and parenchyma percentage was lowest in all the selected species. The selected species were well adapted to xerophytic conditions with low potential hydraulic conductivity and had primitive anatomical characters.</p>