The present invention provides analogues of duocarmycins that are potent cytotoxins. Also provided are peptidyl and disulfide linkers that are cleaved in vivo. The linkers are of use in forming prodrugs and conjugates of the cytotoxins of the invention as well as other diagnostic and therapeutic moieties. The invention provides prodrugs and conjugates of the duocarmycin analogues with the linker arms of the invention.