Since the third edition of this small guide-book was published several more Buddhist sites of importance, including Khāder Mohṛā, Akhaurī, Kālawān and Bhamāla, have been excavated, and much valuable material recorded from them. Moreover, a detailed and comprehensive account of all my discoveries at Taxila between the years 1912 and 1934 has been published in three volumes entitled Taxila (Cambridge University Press, 1951). The further research and co-ordination of data involved in this big undertaking have led to new light being thrown on various outstanding problems. In order to bring this, the fourth, edition up to date and to incorporate in it the extra material, it has been necessary not only to revise and in part to rewrite the existing text, but to increase it substantially by raising the number of chapters from eleven to sixteen and the number of illustrations from twenty-six to thirty-seven.