Bartonella henselae causes most cases of cat scratch disease, a self-limited localised lymphadenopathy illness of humans. Bartonella henselae also causes disseminated cutaneous and visceral disease in immunocompromised people. Cat blood (1-5 ml) collected from cats in the Auckland area was processed and plated on to 5% sheep blood brain heart infusion agar and incubated at 35 degrees C in 5% CO2 for 14 days. Bartonella henselae was identified by colony morphology, Gram's stain, twitching motility, biochemical tests and molecular methods. Eight of 48 cats (17%) had Bartonella bacteraemia. Species-specific probes and biochemical profiles identified all isolates as B. henselae. Infected cats pose a risk to humans they lick, scratch or bite. People should be made aware of the risk cats pose.