This book "Portfolio As a Tool For Assessing On-going Development of Writing Skill" demonstrates how a portfolio can be used to keep record of on-going development of the students' writing skills. It is written based on an action research. Throughout the research students were kept engaged in Creative Writing Process. The Process Writing Approach was adopted and implemented as the major instructional strategy to encourage students to be more imaginative. The students were encouraged to improve their compositions based on self editing, peer editing and teacher's constructive feedback which helped the students improve the composition to a great extent. Critically analyzing students' compositions and giving them constructive feedback helped students improve their writing skills which can easily be seen from students' portfolios. This book also indirectly defines how a teachers can improve his/her teaching skill by becoming a reflective practitioner. This book is beneficial for the teachers who wish to introduce portfolio in their classrooms and develop students writing skills systematically.