In this study we compared the effects of two types of form-focused instruction (FFI) on second language (L2) learning and their potential contributions to the development of different types of L2 knowledge. Both types of instruction were pre-emptive in nature, that is planned and teacher generated. In Integrated FFI attention to form was embedded within communicative practice; in Isolated FFI it was separated from communicative practice. Two groups of adult learners of English as a second language (ESL) received 12 hours of Integrated or Isolated FFI on the 'passive' construction. Learners' progress on a written grammar test and an oral communication task indicated no significant differences between the instructional groups over time. However, some advantages were observed for Integrated FFI on the oral production task and for Isolated FFI on the written grammar test. The results are discussed in relation to instructed second language acquisition (SLA) research and transfer appropriate processing theory.