This book addresses a long-standing problem faced by researchers using occupational information from historical sources in different countries: how to make effective comparisons between nations and across regional boundaries. Occupational data are routinely employed by historians and other social scientists to investigate past patterns and processes of economic and social life. Occupations are in many senses the best, and in some cases the only, available indicators of human capital, industrial development and social structure among national historical populations. Yet some of the most interesting and important questions in fields informed by the history of work, such as mobility research, demography, or the study of labour markets, are comparative ones. Is there, for example, a shared underlying dynamic to modern societies, which makes them more open and wealthier than their predecessors? Up to now, such questions have been difficult to address on the basis of historical evidence because of the variations in meaning within occupational terminology across both time and space. HISCO offers a solution to this problem, providing a common, cross-national, language-sensitive, coding scheme that can accommodate historical occupational titles of the kind found in documents ranging from state censuses to parish records. The HISCO scheme is based on the International Labour Organisation's ISCO68 classification, thereby also facilitating comparison between historical and contemporary datasets. The ISCO68 scheme was adapted and transformed into HISCO by a team of native-speaking, national specialists in work history using large-scale databases from Belgium, Britain, Canada, France, Germany, the Netherlands, Norway and Sweden, which together span the period 1690-1970. In addition to an occupational classification system that organises job titles according to tasks performed, HISCO includes three subsidiary classifications, allowing researchers to take account of any additional information recorded about an individual's status, relationship to the labour market, or the products he or she made and traded. The HISCO book includes a language-based, alphabetical coding index, which shows the - sometime multiple - options available to researchers seeking to place a particular title or description. One particular advantage of this book, designed to assist users who prefer not to begin the coding process with the index, is that all examples of titles from the datasets used to create the scheme are also included under the headings and definitions of the HISCO groups. The classification scheme itself is preceded by chapter which explains the principles underpinning HISCO and outlines the provenance, character and historical background of the international occupational data used to create it.