Objectives: To evaluate the impact of a mobile phone-based, remote monitoring, advanced symptom management system (ASyMS©) on the incidence, severity and distress of six chemotherapy-related symptoms (nausea, vomiting, fatigue, mucositis, hand-foot syndrome and diarrhoea) in patients with lung, breast or colorectal cancer. Design: A two group (intervention and control) by five time points (baseline, pre-cycle 2, pre-cycle 3, pre-cycle 4 and pre-cycle 5) randomised controlled trial. Setting: Seven clinical sites in the UK; five specialist cancer centres and two local district hospitals. Participants: One hundred and twelve people with breast, lung or colorectal cancer receiving outpatient chemotherapy. Interventions: A mobile phone-based, remote monitoring, advanced symptom management system (ASyMS©). Main outcome measures: Chemotherapy-related morbidity of six common chemotherapy-related symptoms (nausea, vomiting, fatigue, mucositis, hand-foot syndrome and diarrhoea). Results: There were significantly higher reports of fatigue in the control group compared to the intervention group (odds ratio∈=∈2.29, 95%CI∈=∈1.04 to 5.05, P∈=∈0.040) and reports of hand-foot syndrome were on average lower in the control group (odds ratio control/intervention∈=∈0.39, 95%CI∈=∈0.17 to 0.92, P∈=∈0.031). Conclusion: The study demonstrates that ASyMS © can support the management of symptoms in patients with lung, breast and colorectal cancer receiving chemotherapy.