Hybrid clones evolved from the 1986 hybridization programme involving 20 Wickham parental clones in 38 cross combinations were evaluated in eight small scale trials. The trials were established at the Central Experiment Station of the Rubber Research Institute of India during 1990. A total of 134 hybrid clones resulted from the various cross combinations were evaluated in the trials. Five hybrid clones viz. 86/392, 86/312, 86/715, 86/911 and 86/887 showed significant improvement for rubber yield over RRII 105. Cross combinations of RRII 203 x RRII 105 and RRII 105 x RRIC 52 were identified as specific families for genetic improvement in Hevea. Hybrid clones were categorized as latex-timber, timber-latex, and latex clones based on yield and timber traits. More progenies with higher timber volume was obtained in majority of the cross combinations, but there were only very few progenies with higher rubber yield from these cross combinations. Bole volume was influenced by girth at opening, and girth attained during tapping. The study showed the superiority of RRII 105 as a female parent in cross combinations for yield improvement rather than as a male parent. Heterosis for girth at opening was observed in seven hybrids. Heterosis for girth in the mature phase was recorded in 20 hybrids. Heterosis for bole volume over RRII 105 was recorded in 69 clones. Meanwhile, heterosis for yield over the standard check clone (RRII 105) was recorded in five out of 134 hybrid clones. Primary clones such as RRIC 52, PB 28/59, PB 86, Gl 1 and RRII 33 and secondary clones (RRII 105, RRII 203 and RRIM 612) are still potential sources for tree improvement in Hevea.