Up to 20% of people with tuberous sclerosis complex develop subependymal giant cell astrocytomas that are usually situated near the foramen of Monroe and commonly obstruct CSF flow, causing hydrocephalus. Operation on these tumours may be hazardous and about a third of patients has an ipsilateral recurrence or contralateral occurrence. Activation of the mammalian target of rapamycin complex 1 (mTORC1) is fundamental to tumour growth in tuberous sclerosis complex, and everolimus inhibits mTOR. A preliminary study showed that treatment with everolimus caused shrinking of subependymal giant cell astrocytomas. Now a trial in Europe, North America, and Australia (Lancet 2013;381:125–32; see also Comment, ibid:95–6) has given support to the use of everolimus for these patients. The trial included a total of 117 patients aged 0–65 years (20 <3 years old, 101 <18 years old) with tuberous sclerosis complex and at least one new or growing subependymal giant cell astrocytoma, or associated new or worsening hydrocephalus, on MRI scanning. Randomisation (2 : 1) was to oral everolimus (with dose titrated to achieve satisfactory blood concentrations) or placebo. A reduction in total subependymal giant cell astrocytoma volume of at least 50% from baseline was achieve in 27 (35%) of the everolimus group but in none of the …