Nontypable strains of Haemophilus influenzae are well-known causes of maternal and neonatal infections. Using DNA-DNA hybridization techniques, some of these strains have been shown to belong to a cryptic genospecies of Haemophilus, which is distantly related to Haemophilus influenzae and Haemophilus hemolyticus. This report describes the first case of sepsis and chorioamnionitis due to Haemophilus influenzae biotype I, which was identified using the RapIDNH system and then confirmed by multilocus enzyme electrophoresis to belong to this cryptic genospecies of Haemophilus. The electromorph type 92 of the isolate was consistent with that of biotype I of the cryptic genospecies.