A cytokinin plant growth hormone kinetin (Kn) retards senescence in plants and delays ageing in human cells in culture. We have now observed that Kn also slows down ageing and prolongs the lifespan of the fruitfly Zaprionus paravittiger when these insects are fed with 25-125 ppm Kn added in their diet medium. In addition, 25 ppm Kn also slows down the larval and the pupal stages of the developing insects. However, the anti-ageing effects of Kn are not merely due to the slowing-down of development, but are mainly due to a reduction in the age-specific death rates throughout the adult lifespan.