Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry is a rapid and accurate tool for the identification of many microorganisms. We assessed this technology for the identification of 103 Haemophilus parainfluenzae, Aggregatibacter aphrophilus, Aggregatibacter actinomycetemcomitans, Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae (HACEK) clinical isolates and 20 Haemophilus influenzae clinical isolates. Ninety-three percent of HACEK organisms were identified correctly to the genus level using the Bruker database, and 100% were identified to the genus level using a custom database that included clinical isolates.