AbstractBackgroundEpidemiological research on late effects of therapy shows the necessity to aggregate chemotherapy agents to substance classes. This requires using conversion factors by substance classes.AimsThe aim of this study was to identify previously used conversion factors from the literature, to present a novel approach for additional factors, and to compare these approaches.Methods and ResultsA literature review was performed, which identified two main principles of deriving conversion factors: effect‐equivalence and equimolar. Thirty‐five articles presenting effect equivalence‐based factors in the widest sense were found in the literature. Ten articles presented the equimolar approach which can be applied to almost all chemotherapy substances. Based on a comprehensive list of treatment protocols used in German pediatric oncology, we derived alternative conversion factors from typical doses. We compared the conversion factors using Pearson correlation coefficients and linear regression. At least two types of conversion factor were available for each of the 49 substances included. The equivalent effect‐based and the typical dose‐based factors were highly correlated with a regression coefficient close to 1. The equimolar factors are independent.ConclusionsFor substances for which no conversion factor based on some type of effect equivalence has been published so far, a factor based on a typical doses‐approach may be used in epidemiological late effects research. Doses aggregated based on the equimolar approach may not be compatible with doses aggregated based on equivalent effects.