Assessment is widely recognised as being inherent in quality teaching and learning at all levels of education (NCCA, 1993, 1999). In recent years the emphasis on assessment has shifted from mainly summative functions to assessment for formative purposes or assessment for learning (Resnick and Resnick, 1992). This period has also seen a shift away from the use of standardised measures of achievement towards the broader concept of authentic assessment and performance assessment from which the portfolio has emerged as a dynamic assessment tool and a locus for reflective practice (Black et al., 1994). This study examines the teaching strategies and attitudes of three teachers of classes junior infants, third-fourth, and fifth respectively, in the greater Dublin area to the teaching and assessment of writing through their engagement with portfolios of children’s creative written work. Data was collected through five methods: (i) semistructured interviews with the teachers; (ii) portfolios of pupils’ writing assembled over a two-year period; (iii) open-ended pupil questionnaires; (iv) standardised test of reading achievement; and (v) observation of classroom practice. Within the portfolio collections three models were studied: working portfolios, documentary portfolios and showcase portfolios (Forster and Masters, 1996). Selected pupils’ work was analysed by qualitative means for evidence of the writing process, for teachers’ instructional and assessment strategies including the use o f feedback in formative assessment. Pupil questionnaires captured student reflections on their work and illustrated their metacognitive knowledge in relation to writing. A framework based on Arts PROPEL at Harvard University (Winner, 1991) was used to assess the portfolios and the student reflections holistically. The study provides evidence for the validity of a portfolio approach to teaching, learning and assessment in writing in the primary school. The study also provides support for the view that effective teaching and assessment of writing is a complex and interactive process, which is not dependent on a particular method or approach (e.g., ‘process’ or ‘skills-based’), but is contingent upon several factors. Critical in the teaching-assessing process is the establishment of clear assessment criteria and the use of feedback in the context of formative assessment. The study raises several issues in relation to models of preservice and inservice teacher education and the influence of school climate in teachers’ ongoing development. The study concludes with a comprehensive review of the implications of these findings for classroom practice, teacher education, and for further research.