Research indicates immersion learners tend to process the second language predominantly for meaning, rather than both meaning and form. Immersion learners appear to be fluent in the second language, but closer scrutiny reveals serious gaps in grammatical accuracy. A study investigated the effect of focus-on-form instruction on the acquisition of agreement features in Spanish within the context of an elementary school immersion science class. Subjects were 63 ten-year-old learners in a two way partial immersion program, in which native speakers and non-native learners of Spanish learn side by side. Specifically, the study investigated whether incidental and implicit oral feedback would affect learners' knowledge of noun-adjective (N-A gender and number) and subject-verb (S-V) agreement in Spanish. Experimental classes received instruction in either N-A or S-V agreement and acted as a control for each other in the feature not instructed. Comparison classes received no instruction. The 6-week treatment period was followed by both immediate and 6-week delayed posttests. Results indicate no significant effect of instruction. Several factors could have contributed to these results: amount and nature of feedback, and inflation of unmarked forms in the data. (Author/MSE)