This article, like others in the Conservation Notes series, is written for the museum professional without conservation training. It briefly covers the nature of skin and hide in chemical and physical terms, the tanning process, deterioration processes, unsuitable treatments, and problem assessment. A table is provided which can allow the curator or collections care person to diagnose the cause of problems with leather objects in the collection based on visible symptoms and characteristics. Finally preventative maintenance procedures such as controlling the storage environment are detailed, as well as the explanation of a dressing procedure for historic leather.