Expression levels of commonly used standards such as actins, tubulins and GAPDH may vary among different cell types (Weisinger et al, 1999) and in response to various factors such as hypoxia and, surgical resection (Thellin et al, 1999; Zhong and Simons, 1999) etc. For example, we observed apparently increased GAPDH mRNA levels in two tumour samples relative to β-actin and to target genes, resulting in down-estimation of the real expression levels of target genes when normalised to GAPDH. The gene discussed is GAPDH; the disease is neoplasm.