The main concern of this report is the nature of the reliance by children on prior native language (L1) knowledge in naturalistic, untutored second language (L2) acquisition. It is suggested that L1 reliance is systematic, in that specific conditions have to be met within the child's L2 development before he or she will, or can, draw on previous L1 knowledge. Therefore reliance on L1 should be predictable within a given developmental sequence. It seems that, in the long run, these predictions may be statable in terms of acquisitional principles in the tradition of Jakobson (1941), Slobin (1973) and Wode (1976). The regularities children follow are those governing language acquisition and determining the structure of developmental sequences. These principles have to be interpreted psychologically and/or neurologically. The main portion of the data, collected daily for six months, came from four German children aged 3 years 11 months to 8 years 11 months. This study concentrates on the acquisition of English negation. (Author/AMH)