Research into complexity, accuracy and fluency (CAF) as basic dimensions of second language performance, proficiency and development has received increased attention in SLA. However, the larger picture in this field of research is often obscured by the breadth of scope, multiple objectives and lack of clarity as to how complexity, accuracy and fluency should be defined, operationalized and measured. The present volume showcases current research on CAF by bringing together eleven contributions from renowned international researchers in the field. These contributions not only add to the body of empirical knowledge about L2 use and L2 development by bringing new research findings to light but they also address fundamental theoretical and methodological issues by responding to questions about the nature, manifestation, development and assessment of CAF as multifaceted constructs. Collectively, the chapters in this book illustrate the converging and sometimes diverging approaches that different disciplines bring to CAF research.