Cyclophosphamide (2H-1, 3, 2-oxazaphosphorine, 2-[bis(2-chloroethyl) amino] tetrahydro-2-oxide) was developed in the search for an inactive "transport" form of the β-chloroethyl group of alkylating compounds. Studies have shown that this compound is relatively inactive in vitro and is converted to the active form in vivo.1-3 Trials in various tumor-bearing animals confirmed this in vivo activity and demonstrated fairly potent antitumor effect.1-5 Preliminary studies in humans suggested that this compound possessed a spectrum of antitumor activity similar to that of other nitrogen mustards, but that it was considerably less toxic.6,7 We have conducted a brief clinical trial of this agent* in a small group of patients with advanced malignancies. This study was not intended to be definitive but was designed to give some indications as to the effective dosage levels and routes, and types and degree of toxicity of cyclophosphamide as compared with the more familiar alkylating agents. Seven