a microbiological study of neonatal conjunctivae and conjunctivitis to investigate the importance of chlamydiae ureaplasmas mycoplasma hominis and anaerobic bacteria in the pathogenesis of neonatal conjunctivitis in the harrow population conjunctival specimens from 104 infants with conjunctivitis and 104 similar healthy neonates were examined the incidence of neonatal conjunctivitis was 82 and no case of neomycinresistant disease occurred during the study staphylococcus aureus viridans streptococci and escherichia coli were the only microorganisms isolated significantly more frequently from affected than from control eyes which suggests that these bacteria may be a cause of the conjunctivitis all cultures for chlamydiae m hominis neisseria gonorrhoeae and anaerobic bacteria were negative the mothers race social status illness and obstetric events were found to have no effect on the incidence time of onset of conjunctivitis or microorganisms isolated the clinical characteristics of conjunctivitis were also not related to the microorganisms isolated no potential pathogens were isolated from 635 of the eyes showing conjunctivitis the results suggest that some of these cases may be caused by chemical irritation and the possibility of an infectious aetiology is also discussed