Intracranial artery stenosis (ICAS) is an arterial narrowing in the brain that can cause stroke. Endovascular therapy (ET) and conventional medical treatment (CMT) may prevent recurrent ischaemic stroke caused by ICAS. However, there is no consensus on the best treatment for people with ICAS.To evaluate the safety and efficacy of endovascular therapy plus conventional medical treatment compared with conventional medical treatment alone for the management of symptomatic intracranial artery stenosis.We searched the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE, Embase, four other databases, and three trials registries on 16 August 2022. We contacted study authors and researchers when we required additional information.We included randomised controlled trials (RCTs) comparing ET plus CMT with CMT alone for the treatment of symptomatic ICAS. ET modalities included angioplasty alone, balloon-mounted stent, and angioplasty followed by placement of a self-expanding stent. CMT included antiplatelet therapy in addition to control of risk factors such as hypertension, hyperlipidaemia, and diabetes.Two review authors independently screened the records to select eligible RCTs, then extracted data from them. We resolved any disagreements through discussion, reaching consensus decisions among the full team. We assessed risk of bias and applied the GRADE approach to assess the certainty of the evidence. The primary outcome was death by any cause or non-fatal stroke of any type within three months of randomisation. Secondary outcomes included all-cause death or non-fatal stroke of any type occurring more than three months after randomisation, ipsilateral stroke, transient ischaemic attack, ischaemic stroke, haemorrhagic stroke, death, restenosis, dependency, and health-related quality of life.We included four RCTs with 989 participants who had symptomatic ICAS, with an age range of 18 to 85 years. We identified two ongoing RTCs. All trials had high risk of performance bias, as it was impossible to blind participants and personnel to the intervention. Three trials were terminated early. One trial was at high risk of attrition bias because of substantial loss to follow-up after one year and a high proportion of participants transferring from ET to CMT. The certainty of evidence ranged from low to moderate; we downgraded for imprecision. Compared to CMT alone, ET plus CMT probably increases the risk of short-term death or stroke (risk ratio (RR) 2.93, 95% confidence interval (CI) 1.81 to 4.75; 4 RCTs, 989 participants; moderate certainty), short-term ipsilateral stroke (RR 3.26, 95% CI 1.94 to 5.48; 4 RCTs, 989 participants; moderate certainty), short-term ischaemic stroke (RR 2.24, 95% CI 1.30 to 3.87; 4 RCTs, 989 participants; moderate certainty), and long-term death or stroke (RR 1.49, 95% CI 1.12 to 1.99; 4 RCTs, 970 participants; moderate certainty). Compared to CMT alone, ET plus CMT may increase the risk of short-term haemorrhagic stroke (RR 13.49, 95% CI 2.59 to 70.15; 4 RCTs, 989 participants; low certainty), short-term death (RR 5.43, 95% CI 1.21 to 24.40; 4 RCTs, 989 participants; low certainty), and long-term haemorrhagic stroke (RR 7.81, 95% CI 1.43 to 42.59; 3 RCTs, 879 participants; low certainty). It is unclear if ET plus CMT compared with CMT alone has an effect on the risk of short-term transient ischaemic attack (RR 0.79, 95% CI 0.30 to 2.07; 3 RCTs, 344 participants; moderate certainty), long-term transient ischaemic attack (RR 1.05, 95% CI 0.50 to 2.19; 3 RCTs, 335 participants; moderate certainty), long-term ipsilateral stroke (RR 1.78, 95% CI 1.00 to 3.17; 4 RCTs, 970 participants; moderate certainty), long-term ischaemic stroke (RR 1.56, 95% CI 0.77 to 3.16; 4 RCTs, 970 participants; moderate certainty), long-term death (RR 1.61, 95% CI 0.77 to 3.38; 4 RCTs, 951 participants; moderate certainty), and long-term dependency (RR 1.51, 95% CI 0.93 to 2.45; 4 RCTs, 947 participants; moderate certainty). No subgroup analyses significantly modified the effect of ET plus CMT versus CMT alone. The trials included no data on restenosis or health-related quality of life.This review provides moderate-certainty evidence that ET plus CMT compared with CMT alone increases the risk of short-term stroke and death in people with recent symptomatic severe ICAS. This effect was still apparent at long-term follow-up but appeared to be due to the early risks of ET; therefore, there may be no clear difference between the interventions in terms of their effects on long-term stroke and death. The impact of delayed ET intervention (more than three weeks after a qualifying event) warrants further study.Copyright © 2023 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.