This study assesses both the social polarisation hypothesis and the role migrants play in this process. The manufacturing sector, once a major source of urban employment and consisting of a large percentage of skilled and semi-skilled, middle-income jobs has declined while the service sector, argued to consist of predominantly either high-skill, high-pay or low-skill, low-pay jobs, has grown. Thus, the decline of manufacturing and the growth of the service sector are argued to result in a more polarised society (Sassen, 1994). Low-wage, low-skill service sector jobs are also argued to attract poorly-educated, unskilled immigrants unable to compete in the urban labour market for anything other than low-skill, low-pay jobs. Thus, the contention is that immigration contributes to social polarisation by increasing the numbers of low-wage workers (Sassen, 1994). However, other scholars hold that the growth of an expanded low-wage service sector is only possible in the face of large-scale migration of these unskilled workers, and that a strong welfare state can militate against the development of a service proletariat (Hamnett, 1994). Using survey and population census data of the Johannesburg region of South Africa from 1970 to 2010, it is shown that, when clerical and service and sales jobs are not misclassified as low-skill work, the growth in these white-collar, middle-income jobs does not contribute to increasing polarisation. Moreover, the numbers of high-skill occupations increased by two and half times as many as low-skill jobs, thereby resulting in a trend of increasing professionalisation of the employed workforce. Shift-share analysis shows that this professionalisation has taken place across all sectors, including the manufacturing sector, and was not confined to the service sectors only. In addition, this relatively smaller amount of low-skill job growth occurred despite large-scale in-migration and the general condition of large numbers of unskilled workers in South Africa. However, economic, and consequently, job growth did not match labour force growth. Even without sufficient welfare provision to discourage workers from taking low-skill, low-wage jobs in favour of unemployment and living on state grants, unemployment grew dramatically in this period as a result of the lack of suitable jobs. In terms of the employed workforce, migrant workers of both sex and all four race groups made significant contributions to the growth in absolute numbers of high-skill jobs. Thus, the increase in high-skill, high-wage and middle-income service sector jobs was that much greater than low-skill job growth, leading to a pattern more consistent with growing professionalisation of the urban workforce, with a concomitant increase in unemployment.