We examined whether the proportion of Shigellae patients among diarrhoeal cases, the distribution, species, case-fatality rates and hospital visits changed over time in Dhaka. We isolated 19639 Shigella strains from 822812 diarrhoea cases treated at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B), between 1969 and 1982. The number of cases increased from 209 (2.5%) in 1969 to 4833 (7.7%) in 1976. Extrapolating from a 4% vigorous systematic sample of ICDDR,B hospital visits shigellosis cases and their proportion among diarrhoea cases increased to more than 9500 (12.0%) in 1981. The prevalence of various shigellae species altered over time. For example: in 1969 Shigella flexneri predominated in 74% of all Shigella cases; in 1973 Shigella dysenteriae accounted for 56%, and in 1981 Shigella flexneri again predominated (75%). More than 20% of all Shigella isolations were from infants: 60% in males and 40% in females. Over 7% of severe cases of Shigella infection referred from the outpatient department and admitted for treatment died. Nearly 40% of all the Shigella deaths were in infants of less than a year old while 49% were in 1-4 year old children. Increasing prevalence of shigellosis appears to be an important cause of diarrhoea in Dhaka especially among children. Areas with poor sanitation and water supply had higher prevalence. However, hospitalized cases represented a fraction of the actual problem. Resistance to antibiotics appears to be increasing and the development of new drugs and preventive methods within economic reach of less developed countries are crucial for reduction of the disease and related deaths.