Introduction: The classification of lung carcinoma is based on small biopsies and/or cytology in 80% of patients with non-small cell carcinoma. However, there is no widely accepted classification system for respiratory cytology. The Japan Lung Cancer Society (JLCS) and Japanese Society of Clinical Cytology (JSCC) have proposed a new four-tiered cytology reporting system for lung carcinoma with the following categories: (1) “negative for malignancy,” (2) “atypical cells,” (3) “suspicious for malignancy,” and (4) “malignancy.” Objective: The aim of this work was to perform an interobserver reproducibility study to confirm the utility of the four-tiered reporting system on respiratory cytological samples. Methods: We analyzed 90 cytological samples obtained with bronchoscopy. Seven observers classified these cases into each category by reviewing one Papanicolaou-stained slide per case according to the three-, four-, and five-tiered reporting systems. Results: The interobserver agreement was fair in the three- (κ = 0.50), four- (κ = 0.45), and five-tiered (κ = 0.45) reporting systems. However, the four-tiered reporting system provided more precise information than the three-tiered reporting system in patient management. The risk of malignancy in the four-tiered reporting system was also stratified well: 19.3% for “negative for malignancy,” 45.6% for “atypical cells,” 74.7% for “suspicious for malignancy,” and 88.1% for “malignancy.” Conclusions: The reporting system proposed by the JLCS and JSCC was designed to enhance the communication between clinicians and pathologists and among different institutions. It is simple and applicable to cytological diagnosis of any respiratory diseases. We propose establishing an international classification for respiratory cytology, harmonizing the reporting systems proposed by different countries.