The neutropenia often seen in infants of hypertensive mothers (IHMs) at < 12 hours of age has been associated with nosocomial infection in the first 18 days of life. To assess maternal hypertension as an independent factor for nosocomial infection, we compared 101 low birth weight (< or = 2.00 kg) IHMs to a concurrent birth weight-matched group of infants of normotensive mothers (INMs). Infants without differential leukocyte counts at < 12 hours of age were excluded, leaving 93 IHMs and 98 INMs. The incidence of neutropenia at < 12 hours among IHMs was not significantly different from that among INMs (42/92 (45%) vs 37/98 (38%)). Nosocomial infection was more frequent in neutropenic IHMs than in neutropenic INMs (12/42 vs 2/37; p = 0.007). Infection in IHMs included omphalitis (2 infants), pneumonia (4), and sepsis with or without meningitis (6); INMs had cellulitis (1) and sepsis (1). The underlying mechanism(s) for this predisposition remains to be elucidated, although limited data suggest that neutropenia may be more severe and prolonged among IHMs.