We have carried out time series photometry of the some young open clusters NGC 1893, Be 59, NGC 7380, Stock 8 and NGC 281 to search for pre-main-sequence variable stars. We have detected several pre-main-sequence variables associated to the young open clusters with periods ranging from ~0.1 to ~50 days. These pre-main-sequence variables could be T Tauri stars. The association of these variable stars with the cluster has been established on the basis of two colour diagrams, a colour-magnitude diagram and spectral energy distributions. The brightness of classical T Tauri stars is found to vary with a larger amplitude in comparison to weak line T Tauri stars. It is found that the amplitude of pre-main-sequence variables decreases with increasing mass, which could be due to the dispersal of discs of massive stars. We have also detected several stars as main-sequence variables, which are classified either as slowly pulsating B stars, β Cep stars, δ Scuti stars or members of a new class of variable stars.