When three diazoacetyl-glycine derivatives, N-diazoacetyl-glycine amide (DGA), N-diazoacetyl-glycine hydrazide (DGI), and N-diazoacetyl-glycine ethyl ester (DGE), were tested against Lewis lung carcinoma in C57BL mice, DGA reduced sharply the number and weight of pulmonary metastases; the effects of DGI and DGE were less pronounced. The growth of the primary tumor was reduced slightly by DGA, but the greater effect was produced by DGI. The absence of correlation between the reduction of the growth of the primary implant and the number of lung secondary tumors for the tested compounds indicated that DGA possesses antimetastatic properties.