Data on reference values of total respiratory resistance (Rint) in healthy people are limited. The aim of this study was to examine the relationship between Rint and gender, height, weight, age and smoking habits. The instrument used was the Jaeger Pneumoscope with a flow interruption device. The method is based on transient interruption of airflow at the mouth for a brief period during which alveolar pressure equilibrates with mouth pressure. Measurement of mouth pressure is used to estimate alveolar pressure prior to interruption. The ratio of this to the flow prior to interruption gives airway resistance. The Rint data were correlated with height, weight, age, gender and smoking habits in 172 healthy subjects. They had a normal lung function (VC, FEV1) and no signs of pulmonary disease. The important determining factor for the value of the Rint were height and age. The mean Rint of 172 subjects was 0.38 +/- 0.17 kPa.1-1.s. The average within-subject variability of repeated measurements of Rint expressed as coefficient of variation was 14.4 +/- 6.9%. Reference equation and normal values for Rint in a healthy population are related to height and age. The measurements were obtained with a commercially available interruption technique.