Garlic sprouts were prepared using the water cultivation method and the constituents of their organ parts were examined. From the cloves, we obtained garlicnin B₁, which is believed to show an antitumor effect, together with E-ajoene and the γ-hydroxybutenolide derivative. The last one was also obtained from the aerial parts and roots, and this was not so far obtained from the native garlics. Garlic sprouts can be considered as useful vegetables as they contain garlicnin B₁ which is presumed to have antitumour effects.