Multiple Myeloma (MM) is a rare blood cancer affecting over 5000 people a year in the UK. All cases of myeloma start with a condition called monoclonal gammopathy of undetermined significance (MGUS). MGUS occurs in approximately 3.2% of people aged 50 and over. Only a small proportion of these people - around 1% each year - will develop myeloma. Most people with MGUS have no symptoms, but a small number of people will suffer complications. This group are referred to as having monoclonal gammopathy of clinical significance (MGCS). People with myeloma frequently experience long delays in diagnosis; the delays are longer than for any other cancer. Although we know that MGUS leads to myeloma, most cases of MGUS are only found 'incidentally' when the person is having blood tests for something else. And the people who have MGUS do not have consistent testing or follow up. This situation means that 80 - 90% of people who are diagnosed with myeloma did not have an earlier MGUS diagnosis. Earlier diagnosis of myeloma might be possible with better understanding MGUS and how it should be monitored. The SECURE study will help with this. It will help confirm the rate at which people with MGUS progress to a diagnosis of myeloma. It will further understanding of screening, diagnosis, and monitoring patterns of people with MGUS and MGCS in the UK. The study aims to find out more about the role of family history and demographic factors in the development of MGUS. It will also find out more about the psychological impact of an MGUS diagnosis and individual quality of life. Patients with MGUS will be identified by their clinical care team and invited to participate in the SECURE study. Participants will be required to answer surveys and questionnaires annually for a period of 5 years or until their disease changes. The study will recruit participants from 20 NHS sites in the UK. Some will be asked to provide blood samples. SECURE is funded by Cancer Research UK (CRUK) and the National Institute for Health Research (NIHR).