Epidemiological features of the epidemic of acute haemorrhagic conjunctivitis in Freetown, Sierra Leone, in 1970, are described. On the basis of hospital figures and a House-to -House survey of 0.9% of the population it is estimated that 50-53% of Freetown's population suffered from the conjunctivitis in 20 weeks. Though no causative agent was isolated, it is supposed, on the basis of the striking similarity with other outbreaks, that the epidemic was caused by enterovirus type 70. Hospital figures, a house-to-house survey and a survey in a closed community provided evidence that man-to-man contact was the principal mode of spread.