Melnick has picked areas for review in the 1971 volume that include viral RNA regulation, antigenic variation of influenzal virus, and the characterization of certain slow virus infections. There is also a resume of investigations on a group of new human respiratory viruses, the coronaviruses, which may be added to the already long list of "common cold" agents. So far these viruses have been isolated almost entirely from adults and, unlike their murine and avian relatives, have not been associated with diseases in other organs. The review of the California arboviruses may be of greater interest to pediatricians. It is now apparent that these agents are responsible for significant numbers of cases of encephalitis, most frequently affecting children and largely from Eastern and middle Western states. In a final chapter the editors present a classification of viruses which includes several groups not recognized five years ago.
In addition to the