31 patients with inoperable non-small-cell lung cancer were treated with Lonidamine at daily doses of 450-900 mg orally. Side effects mostly consisted of myalgias, often severe, and gastrointestinal symptoms. Lonidamine was discontinued in 8 patients because of tumor progression and in 2 on account of side effects. 3 partial responses were observed, 2 in patients with epidermoid tumors.