The incidence of multiple cancer types is increasing in younger generations, with the underlying causes being debated. Here, we propose that environmentally-driven organ enlargement is a novel mechanism contributing to the observed increase in intergenerational cancer risk. All other things being equal, cancer risk will be higher in larger organs composed of more constituent cells, due to the lifetime accumulation of stochastic genomic replication errors. Importantly, the size of certain organs is affected by factors such as diet and lifestyle. Could distinct environmental conditions between generations, therefore, drive organ enlargement, and as a secondary effect, increase cancer risk? Average height and weight-which correlate to the size of internal organs-have clearly been increasing in more recent generations. Recent studies have also found that socio-economic factors are associated with increased brain volume. Research to examine the validity and applicability of the proposed hypothesis could be highly important for public health policy.