This study estimated the incidence of clinical neonatal seizures among infants born between 1992 and 1994 in Harris County, Texas, a county with a large and ethnically diverse population. Infants with neonatal seizures were ascertained from four sources: hospital discharge diagnoses, birth certificates, death certificates, and a study of neonatal seizures conducted concurrently with this study at a large tertiary care center in Houston, Texas. There were 207 cases of clinical neonatal seizures among 116,048 live births (an incidence of 1.8 per 1,000 live births). The incidence was highest among infants weighing less than 1,500 g (19/1,000) and decreased as birth weight increased. There was no significant difference in incidence by ethnicity. Twenty-six percent of the seizures (54/207) occurred after the infants had been discharged from the hospital where they were born. The incidence of neonatal seizures in Harris County was lower than the incidence reported recently for Fayette County, Kentucky, for 1985-1989 (3.5/1,000) and for Newfoundland, Canada, for 1990-1995 (2.5/1,000), but was higher than the incidence estimated for Rochester, Minnesota, for 1935-1984 (1/1,000).