Spontaneous activity of cortical neurons was studied under urethane anesthesia in adult rats 3 months after convulsive status epilepticus induced by lithium-pilocarpine administration at the age of 12 (SE12 group) or 25 (SE25 group) days. Whereas random firing neurons dominated in control animals (61 out of 98 cells), SE25 animals exhibited a significant increase in the incidence of bursting cells (38 out of 59 units). Similar change in SE12 animals did not reach the level of statistical significance. Status epilepticus at an early developmental stage may result in a long-lasting change in functions of surviving cortical neurons.