The present invention generally relates to the large-scale (e.g., greater than 1 kg scale) preparation of low molecular weight polylysine or polyornithine in high yield by preparing a polylysine or polyornithine having a weight average molecular weight from about 12,500 Daltons to about 22,000 Daltons and hydrolyzing it to produce a polylysine or polyornithine having a weight average molecular weight from about 5,500 Daltons to about 12,000 Daltons. In preferred embodiments, the polymer is a homopolymer of poly-L-lysine.