The pre-main-sequence stars and initial mass function of NGC 2264

UBVRI and H alpha CCD photometry has been performed in the southern region of NGC 2264 around the Cone Nebula. A nearly complete list of pre-main-sequ ence (PMS) members in the cluster has been made from the compilation of H a lpha emission stars identified in this study plus those selected in previou s investigations, together with stars with X-ray emission. Using the H-R di agram, we tested a set of four PMS evolution models based on the PMS age an d age spread estimate for the cluster and the mass-age relationship among i ndividual stars. The resultant initial mass function (IMF) is in good agree ment with the field star IMF of the solar neighborhood, with an IMF slope G amma = -1.7 in the mass range 0.3 less than or equal to log m less than or equal to 0.8.