Viral upper respiratory infections, otherwise known as the common cold, are the most common diseases among humans. The self-limited, and often self-diagnosed, acute mild catarrhal illness is usually a nasopharyngitis of 5 to 7 days duration. The major virus groups causing colds are the Picornaviridae, Coronaviridae, Paramyxoviridae, Orthomyxoviridae, and Adenoviridae families. This review will emphasize the basic virology, pathogenesis, and immunology of these infections, and will conclude with present-day and future modalities for treatment and prevention.