Genetic and microenvironmental factors are known to influence tumour metabolism, and these factors vary considerably among patients with non-small-cell lung cancers (NSCLCs). Investigators have now examined the uptake of 13C-glucose intraoperatively in nine patients with NSCLC, revealing that tumour tissues have increase glycolysis and glucose oxidation compared with adjacent benign lung tissues; however, they observed considerable heterogeneity in the metabolic pathways used, both within and between tumours. Multiple alternatives to glucose (such as lactate) were oxidized in all tumours and, unexpectedly, the use of alternative nutrients was common in highly perfused regions of the tumours — where presumably glucose is abundant. These results highlight gaps in our understanding of tumour metabolism.