The effect of P2O5, B2O3 and PbO additives on the sintering and crystallization behaviour of beta .quartz solid solution and gahnite glass-ceramics were investigated. According to our results, only the addition of PbO to glasses produces sinterable glass-ceramics containing beta .quartz solid solution gahnite as the sole crystalline phases, respectively. The nucleation mechanism of the glasses were determined by the Ozawa equation and their activation energy for crystallization were determined by the modified form of the Kissinger, Matusita and Marotta equations. The results indicate that the better sinterability of the lead bearing beta .q.(ss) glass-ceramic than the lead free one could be explained by changes of bulk to surface nucleation and increase of its activation energy for crystallization. At the other hand, it could not be observed any differences between the nucleation mechanism and the activation energy for crystallization of the lead bearing and lead free gahnite glass-ceramics. Then the differences in sinterability of the two glass-ceramics could not be explained by comparison of theirs activation energy for crystallization.