The Allepo Codex dates from the 10th century and is the oldest manuscript of the Old Testament in Hebrew. It was brought to the Israel Museum, Jerusalem, on permanent loan in 1986. The ensuing studies, analytical tests, and conservation treatment were carried out by the Department of Conservation. Conservation efforts took several directions: documentation, microorganism identification, protein fiber analysis and tests, and restoration treatment. The documentation procedures fell into three main groups: detailed examination of condition, making use of the Codex facsimile edition to illustrate the written report, and photography and collation. Several natural synthetic collagen connective tissues were studied and their properties tested and compared. The treatment of the individual leaves of parchment included mechanical and solvent cleaning, the removal of glue and pressure-sensitive tapes, ink consolidation on the vaccuum table, and filling of losses and stretching.