Disease control with compost often is attributed to four factors including competition, antibiosis, parasitism and induced systemic resistance (ISR). Induction of systemic resistance by source separated household waste and yard trimmings compost against Pythium. root rot of cucumber caused by Pythium ultimum was studied in a split-root bioassay. Split-root pairings were tested in root rot potting soil paired with potting soil, compost-amended potting soil suppressive to root rot paired with the potting soil, and compost-amended potting soil paired with the compost-amended potting soil. Only one side of the split roots was infested with P. ultimum. Root rot, based on dry and fresh root weights, was significantly reduced in split roots of plants produced in the conducive infested potting soil paired with the suppressive yard trimmings compost-amended mix. This suggested that systemic effects were induced in the roots by the suppressive compost against Pythium root rot. Growth of transplants germinated in the source separated household waste compost mix was significantly better than those germinated in the potting soil. Finally, root rot of plants germinated in the suppressive mix and then transplanted into the conducive mix was also significantly less severe than that of plants germinated in the conducive mix.