Carcinoma of the esophagus is the most common malignancy in many parts of China. In an attempt to control it by early diagnosis, the balloon sampling technique was developed approximately 20 years ago. This technique is now widely used in China and is accepted as a diagnostic method by WHO. Up to 1979, more than 500,000 people were examined in China. It is routinely used for differentiation between benign and malignant lesions in the esophagus, with an accuracy in the range of 90%. In mass surveys, 73.8% of the cancers detected have been carcinoma in situ and minimally invasive carcinomas. Dysplasias have been shown to progress to invasion by cytologic studies. The utilization of this technique has made possible epidemiologic studies and, thereby, coordination of etiologic research in esophageal cancer. Detection rates of early esophageal cancer by cytologic studies are more accurate than are those with either endoscopic or radiologic methods. The instruments and technique for balloon sampling of esophageal lesions are described, as are the cellular cytomorphology and the diagnostic cytologic criteria applicable to the samples obtained.