Spectroscopic observations of Herbig Ae/Be stars

Together with the multiepoch spectroscopic and photometric data compiled for a large sample of these stars and ages estimated for individual stars by using pre-main-sequence evolutionary tracks, we have studied the evolution of emission-line activity in them. We find that, on average, the H{alpha} emission line strength decreases with increasing stellar age in Herbig Ae/Be stars, indicating that the accretion activity gradually declines during the pre-main-sequence phase.