The tillering rate as influenced by seedling age in two rice varieties was negatively related to initial dry matter up to 35 days after transplanting, and positively thereafter. Between the varieties absolute tillering rate did not differ greatly up to 35 days after transplanting but later on the rate for IR50 was much higher than that of BR14. The absolute tillering rate from 30 days after transplanting and onward for 80-day-old seedlings was comparatively lower than with other seedling ages. IR50 produced more tillers than BR14 in all age groups but within a variety the number of total tillers decreased with seedling age. BR14 required more dry matter to produce a tiller compared with IR50. Younger seedlings required less dry matter to produce a tiller than older ones. Dry matter required to produce a tiller was the highest for tertiary and the lowest for secondary tillers. After transplanting, older seedlings required less time to enter into the booting stage than the younger ones. Percentage of tillers entering into the booting stage was the highest for primary and the lowest for tertiary tillers.