Making the decision whether a patient with chest disease can undergo lung surgery may be easier if the anatomical extent of the disease and the functional effects of resection can be estimated. Although information can be gained by non-invasive physiological studies of lung function of a routine kind, these cannot define the anatomical extent of the disease or distinguish the relative influence of affected and unaffected parts as estimates of lung function. Whole lung ventilation and perfusion scans provide immediate topographic information but have limited resolution and anatomical accuracy, particularly when the architecture of the lung is disturbed by disease. Bronchoscopy gives direct visual information about the more central airways but little or none about the function of the areas they serve. This paper gives brief descriptions of a series of procedures which could help in assessing the feasibility of lung surgery. The size, shape and volumes of individual lungs and lobes can be estimated from plain chest radiographs. Corresponding information about individual segments, and about lobes not delineated by normal X-ray, can be obtained using radio-active krypton 81m and a gamma camera during otherwise routine fibreoptic bronchscopy segments can be determined by simple single-breath manoeuvres at bronchoscopy using a respiratory mass spectrometer. The radio-isotope and spectrometric tests can be obtained in the same breath. The spectrometric tests can be recorded from more than one part of the lung within the same breath. All of the procedures give information in terms of anatomical units of interest to the surgeon.