[en] Epidemiological assessment of the health effects of exposure to low-dose ionising radiation is limited by the need for very large sample sizes and by various sources of bias that may generally affect epidemiological studies. Motivated by the present focus on low-dose effects, the following questions are examined: what are the strictly unavoidable limiting factors in the epidemiological methodology; what is its resolution limit in terms of effect size and what can be done to obtain further supportive evidence from the data? (author)