The common cold is caused by more than 100 virus types. However, the clinical manifestation is always similar with rhinorrhea, stuffiness, sneezing, pharyngitis, laryngitis and cough. The local inflammatory reactions are not due to the presence of virus but caused by locally produced inflammatory mediators. Bacterial superinfections may cause otitis or sinusitis. Bacterial nasopharyngitis has been described in children. This entity possibly exists also in adults. Traditional viral cultures are rarely positive and are not recommended in the daily routine. In children, antigen detection for adenovirus, respiratory syncytial virus, parainfluenza and influenza virus are recommended to confirm the viral etiology or for epidemiological surveillance. The presence of group-A streptococci must be proven by culture or antigen detection before treatment with penicillin. Antiviral treatment is limited to interferon or ribavirin. New antiviral substances are in development. Today, treatment of common cold is limited to symptomatic measures, and antibiotic treatment is not justified.