Described herein are novel 1-aryl-3-(2-chloroalkanylureas derivatives. These derivatives are useful anticaner agents having excellent specifilty towards cell targets and potent antineoplastic activity without systemic toxicity derivatives mutagenicity. More specifically, the invention is directed to novel derivatives of the following formula: ##STR1## wherein R.sub.1 is C.sub.1 -C.sub.6 alkyl, C.sub.3 -C.sub.7 cycloalkyl, C.sub.1 -C.sub.6 alkoxy, C.sub.1 -C.sub.6 hydroxy alkyl, or C.sub.1 -C.sub.6 halide; R.sub.2 is H, C.sub.1 -C.sub.6 alky, C.sub.3 -C.sub.7 cycloalkyl, C.sub.1 -C.sub.6 I alkoxy, C.sub.1 -C.sub.6 hydroxy alkyl or C.sub.1 -C.sub.6 halide, di-halide or tri-halide; R.sub.1 and R.sub.2 may also be part of cyclic structures. R.sub.3 and R.sub.4 are as defined in R.sub.6 or, halide, di-halide, tri-halide, C.sub.1 -C.sub.7 lower dialkyl, or alicyclic groups fused to the phenyl ring, these alicyclic ring can be substituted by one or more groups as defined in R.sub.6 ; or polycyclic rings bearing not more than three rings wherein the rings other than the ring bearing the substituted 2-chloroethylamino moiety can be substituted by one or more groups as defined in R.sub.6 ; R.sub.6 is H, C.sub.1 -C.sub.7 alkyl, C.sub.1 -C.sub.7 alkoxy alkyl, C.sub.1 -C.sub.7 amino alkyl, C.sub.1 -C.sub.6 thio alkyl, C.sub.1 -C.sub.5 S-alkyl, C.sub.1 -C.sub.7 N-alkyl, C.sub.1 -C.sub.7 N,N-dialkyl, C.sub.1 -C.sub.7 cyanoalkyl, C.sub.1 -C.sub.7 haloalkyl, C.sub.1 -C.sub.7 sulfoxide or C.sub.3 -C.sub.7 cycloalkyl; or a prodrug thereof Also disclosed are pharmaceutical compositions containing the compounds of the invention in conjunction with a pharmaceutically acceptable carrier and the use of the compositions in treating cancer.