Published online by Cambridge University Press: 25 September 2002
The main properties of pre-main-sequence (PMS) evolution are reviewed, withparticular emphasis on the impact of star formation studies. I will firstdiscuss the basic results established by the work of Hayashi, Iben andCameron in the early '60s. The changes introduced by the constraintsset by the previously ignored phase of protostellar evolution will bethen addressed. Evolutionary models including a variety of physical effects(accretion, rotation, magnetic field) are presented. Finally, theapplication of PMS models to reconstruct the star formation historiesof clusters and associations will be addressed.