The Myc protein activates transcription as part of a complex with its partner protein, Max. Myc-transformed cells are also characterised by the loss of expression of a number of genes and this repressive effect of Myc on gene expression may not be mediated by the Myc/Max complex. We recently isolated by two-hybrid cloning a novel zinc-finger protein that associates with the carboxy-terminus of Myc. We have termed this protein Miz-1 (Myc-interacting zinc finger protein). Some of the properties of Miz-1 suggest that it may be involved in gene repression by Myc in vivo.