Pediatricians are likely to encounter a limited number of viruses causing a significant number of problems. Many of these infections, such as the common cold, do not currently require specific viral diagnosis. On the other hand, the rapid diagnosis of some viral infections has become clinically and epidemiologically more important as a result of improved understanding of viral transmissability and recent developments in preventive and therapeutic approaches. Concomitantly, several new diagnostic methods have been applied to many of these agents with increasing numbers of commercial kits. This double-edged sword of the predictably greater availability of means to obtain a rapid specific diagnosis of many viral infections, together with the various problems discussed here which can lead to erroneous management of patients, is becoming an important new challenge to the pediatrician.