We review empirical studies bearing on the effects of parasites on the
age of maturity of their hosts. The few cases already published suppo
rt theoretical predictions, namely a decrease of host pre reproductive
lifespan unless parasites are benign. Host responses may be due eithe
r to phenotypic plasticity or io genetic differences, and even though
very few studies on this topic have already been published both mechan
isms occur. Promising areas of research include the distribution oi ag
e-specific potential costs of resistance to parasitism, as well as the
evolution of age-specific parasite preferences under the concomitant
evolution of host life history traits.