Many studies on the Islamic world refer to writings that were originally published in manuscript. Even if a lot of these texts are now available in print, countless others are not, while printed works are often superseded by later, more critical editions. This means that the importance of Islamic manuscripts remains undiminished. In the West, major collections were established before 1900 and it is exceptional for new collections to be founded. In Iran, a country whose libraries host over 345.000 manuscripts, the establishment of new collections, often by testamentary disposition, is not uncommon. The Imām Ṣādiq Madrasa of Chalus near the Caspian Sea was founded in 1948. Its library contained just printed books. From 1979 onward, its third director, Sayyid Jamāl al-Dīn Mūsawī, introduced a programme for the active collection of manuscripts from among the inhabitants of Chalus and the surrounding region. By 2002, some 700 manuscripts had been obtained, all described in this catalogue.