BACKGROUND: Human rhinoviruses (HRVs) have increasingly been reported to be associated with lower respiratory tract infections. HRV-C has been associated with more severe respiratory illnesses in children. OBJECTIVES: We investigated the clinical and molecular characteristics of HRV-A, HRV-B, and HRV-C in adults with pneumonia. STUDY DESIGN: HRV genotyping and quantitative real-time reverse-transcriptase polymerase chain reaction were performed on 392 adult respiratory specimens consecutively collected from June 2012 to May 2013. Pneumonia was identified by review of medical records and chest radiographs. RESULTS: Adult patients with pneumonia and identified HRV genotypes (n=165) were included. HRV-A, HRV-B, and HRV-C were identified in 97, 28, and 40 patients, respectively. No differences in underlying diseases, APACHE II score, or frequency of co-infection were observed between the HRV species. Compared with HRV-A, HRV-B was more often associated with neutropenia (21.4% vs. 7.2%, p=0.07), hospital acquisition (32.1% vs. 7.2%, p=0.048), and fever (78.6% vs. 49.3%, p=0.003). Mean viral load (copies/ml) was lower for HRV-B (10(2.6) vs. 10(4.1) in HRV-A and 10(4.3) in HRV-C), and high viral loads (>/=10(4)) occurred most frequently with HRV-C (70.0% vs. 57.7% for HRV-A and 21.4% for HRV-B). The incidence of severe pneumonia was similar for HRV-A (18.6%), HRV-B (21.4%), and HRV-C (20.0%), and in-hospital mortality rates did not differ significantly (15.5%, 10.7%, and 12.5%, respectively). CONCLUSIONS: In contrast to previous pediatric studies, no differences were observed in clinical severity or outcomes between the different HRV species in adult patients with pneumonia.