The transport of D-glucose, L-phenyl-alanine, L-lysine and L-aspartic acid was measured in the brush border membrane vesicles prepared from intestines of Swiss albino mice infected with three different inocula of Giardia lamblia cysts (100, 1,000 and 10,000 cysts). A significantly low uptake of nutrients was observed in the infected animals as compared with the uninfected groups (P less than 0.05). However, the uptake of nutrients did not alter significantly with varying inoculum size. With D-glucose the respective peak uptakes at 30 seconds were 59.3 +/- 5.5, 60.4 +/- 3.8 and 60.5 +/- 4.02 pmoles mg-1 protein, while with L-phenyl-alanine they were 158.1 +/- 8.3, 151.7 +/- 17.3 and 140.7 +/- 6.0 pmoles mg-1 protein. The same trend was observed for L-lysine and L-aspartic acid. Therefore we conclude that inoculum size does not influence the uptake of nutrients.