Brain-derived neurotrophic factor (BDNF) heterozygous mice (BDNF (+/-)) kindle slowly and have a higher seizure threshold. However, BDNF (+/-) mice exhibit reduced cortical inhibition and disrupted balance of excitation/inhibition synaptic transmission. We investigated penicillin-induced focal cortical epileptiform activity and electroencephalogram (EEG) spectral power of BDNF (+/-) mice, by using electrocorticogram (ECoG) recordings. BDNF (+/-) mice (n = 10) and wild type littermates (n = 9) were anesthetized with i.p. urethane (1.750 g/kg). The recordings of ECoG were carried out by using a data acquisition system and 100 IU penicillin was administered intracortically to induce epileptiform activity. The latencies for the onset of spikes and the amplitude of the spikes showed no differences. However the frequency of the spikes was significantly lower in BDNF (+/-) mice at 40th and 45th min following penicillin injection. Additionally, the EEG power for both BDNF (+/-) and wild type mice reduced after penicillin injection and enhanced during epileptiform activity. The spectral power analysis also revealed that the absolute Gamma power of BDNF (+/-) was significantly smaller than wild types.