A powerful combination of genetics and biochemistry has provided details of how Ras-directed signalling interacts with and is regulated by other cellular signalling pathways. This might ultimately lead to the control of deregulated signalling by oncogenic Ras. Recently, progress has been made in understanding the regulation of Ras-mediated activation of the Raf-1-ERK2 kinase cascade through crosstalk with protein kinase C and cyclic-AMP-dependent protein kinase.