A novel simple nonradioactive method for detection of specific nucleotide sequences has been developed. This method consists of the hybridization of a target DNA with a DNA probe modified with trans-diamminedichlorplatinum(II) (trans-DDP) followed by detection of DNA/DNA hybrids with affinity-isolated anti-DNA-trans-DDP antibodies and poly-horseradish peroxidase-protein A conjugate. Major advantages of this approach are the low cost and the extreme simplicity of the labeling procedure, which involves only mixing of the reagents. The sensitivity of the proposed technique is sufficient to detect 0.8 pg of DNA in Southern blot hybridization and 25 fg in dot hybridization and permits colony screening.