This book explains the concept of Islamic "da'wah", or missionary activity, as it has developed in contemporary Western contexts. Poston traces the transition from the early "external-institutional" missionary approach impracticable in modern Western society, to an "internal-personal" approach which aims at the conversion of individuals and seeks to influence society from the bottom upwards. Poston also combines the results of a questionnaire-survey with an analysis of published testimonies to identify significant traits that distinguish converts to Islam.