isolates tested, 21 of 22 (96%) were resistant to tetracycline, and 18 of 20 (90%) were resistant to cotrimoxazole. Altogether, 18 of 20 (90%) S. flexneri isolates were also resistant to ampicillin in contrast to only 7 of 117 (6%) S. sonnei isolates (P < 0.0001). Similarly 14 of 14 S. flexneri isolates were resistant to chloramphenicol but only 2 of 95 S. sonnei isolates were resistant (Table 1).There was a seasonal pattern of dysentery and episodes of infection with S. sonnei and S. flexneri (Fig. 4). The yearly peak of dysentery and S. sonnei incidence followed the hottest months of the year, April–May, and coincided with the onset of the rainy season. During the summer months of 2001, higher numbers of cases of dysentery and S. sonnei were detected compared with the preceding and following years. The lowest shigellosis rates were observed during the cooler wintermonths, November–March.