We studied a 6-year-old girl who presented with inappropriate and uncontrollable laughing episodes since age 3. Physical examination revealed a precocious puberty. The luteinizing hormone-releasing hormone (LH-RH) stimulation test showed an increased level of follicle-stimulating hormone (FSH). The interictal electroencephalogram (EEG) was normal. Several laughing fits were documented during video/EEG monitoring. During laughing, the ictal EEG showed a diffuse suppression of background rhythm, prominent over the left mesial temporal region. A mass lesion about 2 x 2 cm in size was found over the suprasellar cistern with a broad base attached to the hypothalamus, which was isodense on a computed tomography (CT) scan, isointense to gray matter on T1-weighted magnetic resonance (MR) imaging and hyperintense on T2-weighted MR imaging. The findings were suggestive of a hypothalamic hamartoma. A variety of anticonvulsants had been used with little or no response to the frequency or duration of the laughing seizures.