The association between the molar ratio of IGF-I/IGFBP-3 and breast cancer risk was similar to that of IGF-I adjusted for IGFBP-3 (OR 1.61; 95% CI: 0.75–3.47 in the highest vs the lowest third of IGF-I/IGFBP-3 concentration; test for linear trend; P=0.19). The gene discussed is IGF1; the disease is breast carcinoma.