Azelaic acid (AzAc) is a C9 dicarboxylic acid which has recently been shown to have some therapeutic applications in skin diseases of different aetiologies. In order to study the in vitro activity of AzAc five human malignant melanoma primary cell cultures were treated for up to 60 days with 10 mM C9 2Na; the growth characteristics were defined by growth curve and the cytogenetics by Giemsa standard technique and GTG banding technique. Our data demonstrated an inhibition in replication of all five melanomas and the disappearance of the clones with chromosomal markers in four out of five melanomas after AzAc treatment.