Effects of rotation on the PMS evolutionary tracks in the HR diagram for 1 M_⊙ models. The dotted and continuous lines correspond to a non-rotating model and a rotating model computed with a full treatment of shellular rotation, respectively. The track corresponding to a rotating model including only the effects of rotational mixing is shown by a dashed line and is superimposed on the track of the non-rotating model. The tracks end when the ZAMS is reached; the end of the disc-locking phase is indicated by a triangle.