Cancer is currently the leading cause of death in Belgium, accounting for ca. 27.000 yearly deaths. Despite an abundance of medical research, the history of cancer (victims) is basically unwritten. Since the mid-19th century, a significant increase in cancer mortality has been observed in many Western countries. This rise can be framed within the so-called epidemiological transition: in the past two centuries infectious diseases (cholera, TB, etc.) as main causes of death were gradually replaced by degenerative diseases such as cancer. However, we do not know how the cancer transition occurred. By using a mixed-method approach and drawing on unique causes-of-death registers and qualitative sources such as medical journals, I aim to unravel the spatial and socioeconomic inequalities of cancer mortality in Belgium between 1821 and 1991. How did cancer mortality vary according to age, sex, occupation and origin? How did spatial disparities in cancer mortality relate to local and regional living conditions? and, what did people know about cancer? Highly urbanized Belgium, one of the first countries to industrialize, is an ideal case study to examine how cancer mortality inequalities developed since the 19th century. My project will contribute to three major international debates: 1) discussions on the emergence and historical development of mortality inequalities, 2) knowledge of the cancer transition, and 3) our understanding of current cancer mortality inequalities.