Phytochemical studies on the aerial parts of Withania somnifera L. Dunal. (Solanaceae) led to the isolation of a chlorinated steroidal lactone (27-acetoxy-4β,6α-dihydroxy-5β-chloro-1-oxowitha-2,24-dienolide), a diepoxy withanolide (5β,6β,14α,15α-diepoxy-4β,27-dihydroxy-1-oxowitha-2,24-dienolide), and withaferin A. Their structures were elucidated by using spectroscopic techniques. All three compounds exhibited a growth inhibition and cytotoxic activity against human lung cancer cell line (NCI-H460), with withaferin A being the most potent (GI 50 =0.18μg/mL and LC 50 =0.45μg/mL) among three compounds tested.