Five studies were aimed at furthering understanding of the effects of second language immersion on young children. The first study demonstrated that the neuropsychological test profile of children who are unable to make satisfactory progress when immersed in a kindergarten second language program is different from that of children with more "traditional" learning disabilities, and that the learning-disability profile of the immersed group was distinguishable from that of other groups. A second study confirmed these results and demonstrated that the neuropsychological deficits in question were no longer found after nine years of age. A sample of children was assessed at the end of the first and second years of kindergarten and of grade 1. These three assessments indicated that it was possible to identify with 100% accuracy, based on the first year's assessment, the children who would drop out of French immersion for academic reasons. The best predictors were the individual neuropsychological measures. The test findings support the interpretation of the first two years' studies that attributes the failure of young children (with no apparent disabilities) to succeed in immersion programs to a mild maturational lag, which does not affect normal progress in education in the vernacular. (Author/JB)