Pediatric acute subglottic croup is generally of limited duration (usually 2 to 7 days) and caused by influenza or parainfluenza viruses. Prolonged infections may involve other pathogens. To date and to our knowledge, there has been but a single case report of herpes simplex virus type 1 (HSV-1) infection prolonging croup attributed to prolonged use of corticosteroids. Other authors have reported a wide range of HSV-1 infections of the upper and lower respiratory tracts in all age groups that are usually associated with immunocompromise. Two immunocompetent toddlers with prolonged croup associated with HSV-1-positive subglottic lesions are described herein. In one case the culture was obtained 11 days after just three doses of dexamethasone treatment. In the second case the culture was obtained after 10 days of prednisone therapy; the infection cleared quickly following treatment with acyclovir and rapid taper of the prednisone dose. These cases suggest that prolonged croup-like symptoms warrant thorough airway evaluation. Herpes simplex virus type 1 should be a suspected pathogen in cases of prolonged or atypical croup. Herpes simplex virus type 1 croup is not necessarily associated with immunocompromise or prolonged corticosteroid therapy. Acyclovir seems to be effective in treating other airway HSV infections, and by analogy it is the treatment of choice in recalcitrant herpetic croup. It is unknown whether HSV-1 represents a primary or secondary pathogen in prolonged croup.