This hypothesis is supported by a small number of cases in which overexpression of ERβ RNA has been found in Tamoxifen-resistant tumours (n=9) when compared with a Tamoxifen-sensitive group (n=8) (Speirs et al, 1999), but refuted by an immunohistochemical study (Mann et al, 2001) of ERβ protein in a larger group (n=118). The gene discussed is ESR2; the disease is neoplasm.