We report the cases of a 4-year-old Chinese boy and a 33-year-old Chinese man with prodromal constitutional symptoms followed by eruption of small, painless, erythematous, papular lesions on relatively medial aspects of the anterior chest but not as far as the periflexural regions. Spontaneous remission was seen 2 and 3 weeks after rash onset in the child and the adult, respectively. We believe that the terms unilateral mediothoracic exanthem and unilateral thoracic exanthem are appropriate diagnostic labels. Such labels carry clinical significance as the patients can be reassured that although the rash may persist for weeks, final spontaneous remission with no complication is highly likely. Moreover, the risk of contagiousness is low, and we did not insist on isolation for prolonged periods.