The probability to find a correct diagnosis by cytological examination of sputum and other pulmonal specimens sent in to a cytological central laboratory far from comprehensibly seems to render somewhat lower than by histologically examining tissues. The cytologist must try hard to avoid false positive judgments, for the method soon falls into disrepute if false positive reports are sent out. The main source of false positive diagnosis seems to be a too subjective interpretation by the cytopathologist. Basal cell hyperplasia and atypical squamous metaplasia are the main morphologic alterations that may occasionally mislead even an experienced cytopathologist. Inquires to clinics and practice concerning an evaluation on value of sputum cytology to detect bronchogenic cancer proved a high appreciation of this method.