The main role of industrial accident compensation insurance is to protect injured workers and their families by providing various benefits. If a certain disease occurs due to work, the worker must prove the causal relationship between the work and the disease, although it is not easy for injured workers to do so. The epidemiological approach to causality is based on a comparison of the incidence rate in exposed and non-exposed groups. Recently, some arguments have been made regarding the application of epidemiological causality in litigation related to tobacco and some environmental-related diseases. The 3 main points of dispute are as follows: 1) the distinction between specific and non-specific diseases and causal inference, 2) the relative risk and the attributable fraction of the causative factor for the related disease, and 3) the application of population-level epidemiological study results to individual causation. Until now, the main approach to the causality of occupational diseases has been proximate causal relationships because of the practical difficulties in applying epidemiological causality to all events. As coverage under the Industrial Accident Compensation Insurance Act expands, the application of epidemiological causality must be considered, as well as the expansion of applicable occupational diseases. Moreover, doing that could provide enough evidence for managers and workers to take steps to prevent occupational disease. The safety net provided by industrial accident compensation insurance for protecting injured workers needs to be implemented on the basis of scientific evidence.