The age of young NR Hevea trees has an influence on the size of latex particles. Young seedling trees aged less than 3 year had small rubber particles of sizes less than 1mm, while mature trees showed particle sizes of up to 4mm (from 0.04mm to 4 mm). NR latex particles from virgin trees of clones RRIM 600, aged from 1 to 7 years showed the average particle size distribution of about 0.30 mm to 0.65 mm. The average molecular weight (Mw) dramatically increased from 3.3 X 10 5 to 12.0 X 10 5. The polydispersity (Mw/Mn) or molecular weight distribution of rubber was remarkably wide, between 3 and 10. Different clones of 25-year-old (NATAWE 208, AVROS 2037, RRIC 6, GT 1, PR 255, PR 261 and KRS 156) regularly tapped trees presented mode average particle sizes of about 1.0 mm. The average molecular weight (Mw) was from about 6.7 X 10 5 to 3.0 X 10 6 and the polydispersity (Mw/Mn) was extremely extensive between 5 and 11.