Specific antibody titres of colostrum and breast milk from 208 healthy women of Puriscal, a rural area of Costa Rica, were determined by enzyme immunoassays. Mean relative IgA titres of 790 ± sd = 640 (ranges = 70–3250), 440 ± 490 (40–2940), and 280 ± 230 (10–1000) to Shigella flexneri, Shigella sonnei and Shigella dysenteriae type 1 lipopolysaccharides (LPSs), respectively, were found in colostrum on day 1 post delivery. Titres declined there-after and only relatively low values were found on days 30, 90 and 180 post partum. Mean IgA anti-invasion plasmid antigens (Ipa) titres of 200 ± 230, 140 ± 170 and 120 ± 190 on days 1–2, 3–4 and 5–8 post delivery were found, respectively. Thereafter the anti-Ipa titres were low. IgM antibody titres were found against the LPS antigens but not to the Ipa. IgG antibody titres were low against both LPS and Ipa, with the exception of four out of 59 (7%) at day 1, with titres to the S. flexneri Y LPS and three out of 59 (5%) at day 1 and one out of 87 (1%) at days 3–4, with positive IgG titres to Ipa. By using a cut off value (mean +2 sd established for a high socioeconomic status group of Costa Rica), 20%, 17% and 5% of colostrum samples, at day 1, had high titres to S. flexneri, S. sonnei and S. dysenteriae, respectively. A good degree of correlation between colostrum IgA anti- S. flexneri Y LPS and the anti-Ipa antibodies, was found. The colostrum antibody titres (day 1) of mothers from Puriscal were intermediate as compared to mothers from the low and the high socioeconomic conditions in the metropolitan area of Costa Rica and tended to be lower than in Vietnamese mothers from endemic areas of shigellosis. Shigella exposure seems to be lower in this rural region than in overcrowded slums of San José, Costa Rica.