This working paper deals with the ethical dimension of measuring irregular migration. It aims to support the upcoming development of handbooks as main outputs of the MIrreM consortium. Notably, it provides a preliminary basis for the consideration of ethical aspects in measuring irregular migration and identifying regularisation possibilities. The complexity of migration processes, the transitory and uncertain feature of expertise and migration policy dilemmas pose challenges for ethical appraisals. The paper outlines the relevant legal regulations and sectoral codes of ethical conduct that confine research integrity and provide guardrails for an appraisal of ethical risks linked with breach of private data protection requirements, scientific shortcoming related to statistical and algorithmic biases, and impacts of research causing harm to individuals, groups, and society. The paper concludes with a suggestion of a systematic ethical benchmarking approach for the handbook development.