Human promyelocytic leukemia cells,. HL-60, were treated with cisplattn [cis-diamminedichloroplatinum (II)] (2 itiM, 1 h). DNA- eisplatin-protein complexes were isolated and exposed to thiourea (1M), NaCN (100 mM), diethyldithio-carbamate (500 mM), or tf-methyl-D- glucamine dithiocarbamate (500 mM) for 12 h. The release of platinum was measured by atomic absorption spectroscopy. Sodium cyanide was the most effective agent, releasing about 90% of the DNA-bound platinum. Thiourea was the least effective agent, while dithiocar- bamates exhibited an intermediate. The ability of the same group of agents to split the proteins off from the protein-cisplatin-DNA complex was also evaluated and similarly dithiocarbamate were also the most effective.