Two cases of infant chlamydial pneumonia are described, both associated with severe apnoea. In one, the apnoeas occurred in association with seizures. All symptoms resolved rapidly upon treatment with erythromycin. Specific diagnostic tests are available for this condition. One unit in this country has demonstrated a vaginal carriage rate in pregnancy of 4%. The rate is higher in subgroups with overt promiscuity. Efforts at primary prophylaxis should be directed at high risk groups. Every effort should also be made to improve the secondary prophylaxis of chlamydial pneumonia by identifying and adequately treating newborn infants with chlamydial conjunctivitis.