Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma cell disorder which precedes multiple myeloma (MM), an incurable blood cancer. To date, limited research has focused on the psychosocial impact of receiving a MGUS diagnosis. This dissertation reports the findings from an exploratory-sequential mixed methods programme of work conducted to explore the lived experiences of MGUS patients with comparison to other premalignant conditions. To enable comparison with other premalignant conditions, a mixed methods systematic review investigating the psychosocial impact of being diagnosed with a premalignant condition was conducted. A total of 75 studies (21 qualitative, 53 quantitative questionnaire based and one mixed methods studies) were included with quantitative data pooled using random-effects meta-analysis and qualitative data using meta-synthesis techniques. From the meta-synthesis, several themes were evident such as poor information provision, heightened anxiety post-diagnosis and unmet support needs. In contrast, no significant differences in quality of life measures were observed among patients with premalignant conditions compared to controls in pooled analysis of generic QoL or psychosocial wellbeing instruments. Three separate studies focusing on MGUS were undertaken to investigate the viewpoints of MGUS patients and healthcare professionals (HCPs). The first study described is a qualitative study involving focus groups and individual telephone interviews with 14 MGUS patients undertaken in Northern Ireland to investigate the impact of receiving a MGUS diagnosis from a patient perspective. Transcripts were analysed using inductive thematic analysis. From this study three main themes were identified: (1) Experiences of MGUS health services, (2) The psychosocial impact of an MGUS diagnosis and (3) Knowledge of MGUS. These findings indicated unmet needs for MGUS patients; which left patients isolated and confused post-diagnosis. The second study reports on findings from a paper-based cross-sectional survey carried out among haematology HCPs (such as haematologists and specialist nurses) attending an all-Ireland haematology conference to explore the words and language used to describe MGUS to patients at their diagnosis. They used terms such as a “blood condition” or compared it to "like a mole we need to watch". A total of 54 HCPs including 13 from Northern Ireland and 41 from Republic of Ireland responded to the survey. This study found that haematology staff attempted to use lay language to explain the diagnosis to patients and informed the majority of patients about their risk of progression to cancer. Less than half give out an information booklet to all patients and all believed that MGUS patients should be followed up; with the majority wanting haematology to provide care rather than primary care. A separate online survey of GP/ GP trainees was undertaken to investigate GP/GP trainee knowledge of MGUS. The survey was promoted online using social media and the WONCA Europe Conference. A total of 58 GPs and GP Trainees from 25 countries responded. Overall, low levels of MGUS knowledge were observed for both GPs and GP trainees and the majority (88%) stated that they would not be confident in speaking with newly diagnosed MGUS patients. The increased risk of haematological malignancies was identified by 62.1% of GPs/GP trainees with MM, lymphoma and myelodysplastic syndromes the most commonly reported cancers associated with MGUS. The need for MGUS focused information and education resources for GPs was also highlighted. Data from the previous studies was triangulated to develop an online mixed methods instrument to assess QoL and psychosocial wellbeing of premalignant patients; including MGUS (n=171) and smouldering multiple myeloma (SMM) (another premalignant plasma cell disorder) (n=60) patients. The survey was promoted using social media and online patient support groups and included validated instruments such as EQ-5D, SF-12, EQ-5D and HADS. The main findings identified a significant decrease in QoL and psychosocial wellbeing (including increased levels of clinically relevant anxiety and depression) for MGUS patients compared to population norms and SMM patients. Qualitative analysis also indicated that MGUS and SMM patients lived with the fear of a future progression to cancer and a lack of both informational and psychosocial support from both their peers and their healthcare professionals. However, MGUS patients reported more detrimental effects of their diagnosis due to the higher levels of uncertainty and reported more concerns about their surveillance. In summary, the studies included within this dissertation suggest that for some patients MGUS can have a significant psychosocial impact. This dissertation recommends the development of informational resources for clinicians and patients to help inform about MGUS, and better availability of peer and health service support for MGUS patients.