Caspase activity and apoptosis are promoted using active, dimeric Smac peptide mimetics of the general formula M1-L-M2, wherein moieties M1 and M2 are monomeric Smac mimetics and L is a covalent linker. Target cancerous or inflammatory cells are contacted with an effective amount of an active, dimeric Smac mimetic, and a resultant increase in apoptosis of the target cells is detected. The contacting step may be effected by administering to a pharmaceutical composition comprising a therapeutically effective amount of the dimeric mimetic, wherein the individual may be subject to concurrent or antecedent radiation or chemotherapy for treatment of a neoproliferative pathology.