Activation of the proto-oncogene c-fos in the brain was described initially almost a decade ago and represents one of the most studied immediate early genes in the brain. Transient c-fos expression in the central nervous system was first observed after seizure activity and following noxious stimulation in the spinal cord. Since then, multiple studies have shown that different stimuli can induce c-fos expression. Seizure activity induces rapid and transient expression of c-fos in hippocampal structures. Similarly, transient activation of c-fos follows cortical brain injury in a pattern that resembles that of spreading depression. Many other stimuli have been shown to induce the expression of this proto-oncogene in the brain and c-fos immunostaining and in situ hybridization are now used to map brain metabolism under different physiological and non-physiological conditions. Here we review the variety of inducible patterns of c-fos expression in the brain.