In the present study, we show that there is a specific multiplicative interaction between female sex and PNPLA3 p.I148M in determining FLD in at-risk individuals (steatosis and fibrosis, P < 10−10; advanced fibrosis/hepatocellular carcinoma, P = 0.034) and in the general population (P < 10−7 for alanine transaminase levels). The gene discussed is PNPLA3; the disease is steatosis.