Gel precipitation reactions determined antibody isotypes in bile from hens differing in dietary efficiency. Ouchterlony double diffusion employing alpha-chain specific goat-anti-chicken IgA, rabbit anti-chicken IgG, goat anti-chicken IgM, black turtle bean (BTB), and Jacalin lectins as precipitating reagents detected bile IgA, IgG, and IgM from Salmonella exposed and nonexposed hens. The IgA was present in 1 of 3 forms designated by reagent and frequency: IgAB (precipitated by BTB lectin) 100%; IgAA (precipitated by anti-alpha chain antibody) 98%, and IgAJ (precipitated by Jacalin) 97%. That both BTB and Jacalin precipitates contain IgA was confirmed by immuno-dot blots using affinity purified alpha-chain specific antibody, establishing each as IgA glycoforms. Three measurements of Ouchterlony precipitates were made; d1 and d2 indicate diffusion from sample or reagent wells, lambda indicates arc length. Mean values for lambda, estimating quantity, were IgAA (11.3 mm) and IgAB (11.6 mm) and IgAJ (8.3 mm). The crescent shape IgAJ arc and its slower diffusion (d1) suggested its molecular weight is greater than either IgAA or IgAB. Arc lengths of individual samples were not significantly correlated suggesting that these are independent components of bile. Oral Salmonella enteritidis challenge resulted in a highly significant difference in bile IgA profiles. The IgAJ arc lengths (lambda) in R- hens increased by 20% over those in nonchallenged R- hens. Conversely S. enteritidis challenge was associated with a decrease of 10% in IgAJ arc lengths in nonefficient (R+) hens. Salmonella enteritidis challenge was not associated with arc length differences in either IgAA or IgAB. The IgG was present in all specimens, and in 9 of 59 (15%) 2 forms were detected. The IgG quantity was unaffected by either efficiency type or S. enteritidis challenge. The IgM was detected in only 2 of 59 (3.4%) specimens. Our observations suggest IgA of bile is composed of multiple forms influenced both by diet efficiency status and S. enteritidis exposure. It appears that the latter resulted in an increased quantity of IgAJ in R- hens, and suggests the existence of functional differences among the various IgA types.