Success in learning a foreign language is influenced by both affective and cognitive factors. One of the most widely accepted affective factors in foreign language learning is motivation. Motivation is the most used concept for explaining the failure or success of a language learner. Considering the significance of motivation in second language acquisition,this book investigated the effect of motivational factors on English achievement. The wider concluding argument of this book is that motivation, and its constructs are context dependent and therefore, any language learning context has its own unique motivational model. "Thank you for the summary of your research. It is very interesting". R. C. Gardner, Ph.D. Professor Emeritus Department of Psychology University of Western Ontario, "Hojat Jodai has done a very systematic research using the most interesting statistical analysis. I surmise that the study is good enough to be a source of several academic paper publications". Amir Mahdavi Zafarghandi PhD. graduate of Essex University, U.K. Assistant Professor, English Language Dept., University of Guilan, Iran