Photochemistry and Photobiology of Nucleic Acids: Volume II, Biology is a collection of papers that deals with the biological effects due to stable UV induced alterations in critical cellular macromolecules, including cell death, growth delay, mutagenesis, and carcinogenesis. The papers assume that DNA is the macromolecule most relevant to cell pathology, as well as to the photochemical and photobiological properties of RNA which are essential in cellular functions. One paper investigates the UV-induced cross-linkings of proteins with nucleic acids as a possible cause of biological effects other than just in terms of the damage done to nucleic acids. Other papers discuss the mechanisms of protection against, and in the repair of damage caused by UV photons and by ionizing radiation (also chemical mutagens) in many organisms from viruses to mammalian cells. The repair processes appear to play a role in monitoring and preserving the structural integrity of DNA during physiological processes such as replication and transcription. One paper notes that in experiments on human embryonic lung fibroblasts WI-38 at very high radiation doses, radiation products of Thy in acid-soluble form appear while products from the DNA (acid-precipitable fraction) disappear. The paper suggests that the excision process is therefore selective. The collection is suitable for biochemists, microbiologists, or academicians whose works involve genetics, cancer, and cellular research.