The September 2017 issue of Migration Policy Practice focuses on irregular migration and, in particular, on new ways to collect and analyse data in this major policy area. The lead article, "Measuring unsafe migration: The challenge of collecting accurate data on migrant fatalities" by Ann Singleton, Frank Laczko and Julia Black, critically examines the quality of data and the often-publicized figures on migrant fatalities in order to promote a better understanding of the available information. First, it examines the methodology of the International Organization for Migration (IOM) Missing Migrants Project (MMP), currently the only existing database on global migrant fatalities. It then discusses the challenges of collecting data on migrant deaths and disappearances. Finally, the paper presents recommendations for the improvement of data on migrant fatalities.