Objective Toinvestigatetheeffectofelectrochemical therapy (ECT) in the treatme Methods Three hundred and eighty-six cases (287 males and 99 females aged 25 - 78, with an average age of 51 years) with middle and late-stage lung cancers were treated with ECT. Two hundred and three patients had squamous cell carcinoma, 138 adenocarcinoma and 45 undifferentiated cancer. Diameters of the cancers were respectively 4.0-6.0 cm in 153 cases, 6.1-8.0 cm in 82 cases, 8.1-10.0 cm in 102 cases and over 10.0 cm in 49 cases. In this group, none was at stage I, 103 cases were at stage II, 89 cases at III a, 122 cases at III b and 72 cases at IV. Of the 386 cases, 152 cases (39.4%) also suffered from hypertension, heart disease etc. Anode and cathode platinum electrodes were inserted accurately into the tumour mass. Distance between two electrodes was 2.0-2.5 cm. Electrodes were connected to a special ECT instrument. The current was maintained al 6-8 V and 80-100 mA. One hundred coulombs are used for treating 1 cm diameter oi tumour mass. Results Of the 386 cases, 99 cases (25.6%) achieved complete remission (CR), 179 cases (46.4%) achieved partial remission (PR), 59 cases (15.3%) had no change (NC:) and 49 cases (12.7%) had progression of disease (PD). Effective rate (CR + PR) was 72% (278 cases). One to five year survival rates were 86.3%, 76.4%, 58.8%, 39.9% and 29.5%, respectively. Conclusions ECT is easy to use. It is effective, safe, less traumatic and makes patients recover quickly. This is a new and effective method to treat patients with tumours who are inoperable and can not receive chemotherapy or radiotherapy.