Various 32P-postlabelling methods have been evaluated for the detection of melphalan-DNA (mel-DNA) adducts in melphalan treated calf thymus DNA and human blood treated in vitro with melphalan. When the butanol extraction procedure was used for the postlabelling studies, increasing adduct levels were seen between 0.01 and 1.0 micrograms/ml melphalan (maximum adduct value = 3.29/10(8) nucleotides at 1.5 micrograms/ml melphalan). The labelling efficiency, however, was thought to be low. Human blood treated in vitro with a dose range of melphalan from 0.01 to 1.5 micrograms/ml was analysed for micronuclei, sister chromatid exchanges, chromosome aberrations and DNA adducts. A correlation was seen between mel-DNA adducts and cytogenetic damage for each of the endpoints studied.