English-speaking children and adults who were learning Dutch at school and at work, without signigicant amounts of foreign language instruction, were tested at five-month intervals during their first year in Holland. The test battery included tests for active and passive control of phonology, morphology, syntax and vocabulary. Significant improvement occurred during the course of the year on all tests for subjects from all age groups. No age differences were observed in speed of acquisition for the phonology tests, nor did the English speakers reach native-like performance on these tests during the period observed. The tests reflecting knowledge of rule systems, i.e., morphology and syntax, did show large age differences, in all cases favoring the teenage group and with the youngest children scoring worst. The subjects achieved near-native performance on these tests during the period studied. (Author)