This thesis is based on an investigation to find out in what way 40 Swedish public librarieskeep and preserve their library materials. The investigation is based on inquiries sent outto the libraries. It deals with the keeping of books with regard to external factors which havedestructive effects on library materials as well as the safety at the library buildings. It is, aswell, about the preserving work being done at the libraries.Comparisons are made with literature and accounts about preserving measures and recommendationsregarding appropriate environment in premises and depositories. The resultsshow great differences between the libraries as to the library environment, i.e. from payingattention to the factors and taking measures to taking no measures at all. The safety concerningtheft and fire varies as well.Most of the libraries have old and/or special collections. Nearly all the libraries do simplerepairing themselves, while over half the number, in addition, apply to special firms for bindingor more advanced restoring work. Topicality, currency and the last volume are essentialcriteria of book preservation. There is an urgency to preserve local collections and valuableold materials as well.