More recently we developed several transgenic lines that express Myc via haemopoietic-specific regulatory elements from the vav gene.42, 43 The tumour phenotype of the vavP-MYC mice varied between lines, depending on the level of Myc achieved: high expression resulted in rapid-onset T-cell lymphomas whereas low expression resulted in late-onset myeloid tumours and intermediate levels produced both tumour types. The gene discussed is VAV1; the disease is neoplasm.