The yield performance of selected planting materials over three time periods was assessed. Among the 32 planting materials for which data are available, 15 popular ones are selected for the purpose of analysis. The analysis of yield data shows that PB 28/59, RRIM 605, PB 5/51 and GT 1 are found to be superior compared to others in terms of yield (kg ha -1 y-1) during the first ten years of tapping. During the fifteen year period of exploitation among the 8 planting materials, RRIM 605 PB 5/51 and RRIM 623 had relatively higher yield compared to others. Among the four planting materials for which data are available, during the twenty year period, GG 2 topped the list. A multiple regression anlaysis of the available data suggests that the variation in yield can be explained from 64 to 87 per cent (in 20 year period). 76 to 98 per cent (in 15 year period) and 74 to 100 per cent (in 10 year period except in the case of PB 235) depending on the planting material. The observed and estimated yield are comparable except for the first year of tapping for the three time peirods and for the twentieth year of tapping. The planting policy of the company (1970-1980) appears to be in tune with the yield performance of the selected planting materials during the ten year period. During the period 1960-1980 (except for the first sub-period) the clones such as GT 1, PB 28/59, PB 217 and PB 235 have received maximum attention.