Abstract Background/Aims The NIHR Immune-mediated inflammatory diseases (IMID)-Bioresource is a recallable resource of patients with an IMID, pre-disease states and unaffected first-degree relatives. Here, we report on the recruited cohort to date, focusing on co-existent comorbidities. Methods Patients are categorised into one of three primary IMID groups: rheumatoid arthritis (RA), axial-spondyloarthropathy-psoriasis spectrum (AxSpA-PsO: AxSpA, PsO, psoriatic arthritis [PsA], reactive arthritis) and systemic autoimmune rheumatic diseases (SARDs: systemic lupus erythematosus [SLE], mixed and undifferentiated connective tissue disease). Data were collected on clinical phenotype, secondary IMIDs, medications and key co-morbidities. Results 5028 participants (4965 IMIDs, 46 pre-disease, 17 relatives) have been enrolled to the IMID-Bioresource Sept-2020-Aug-2022 from 63 UK-centres. Of those with a diagnosed IMID, RA (N = 2472) was the largest group, then AxSpA-PsO (N = 2012) and SARDs (n = 479). Two-thirds (N = 3210, 64.7%) female, median (IQR) age 57.9 (47.3-67.6) years. 1544 (62.5%) patients with primary IMID RA were seropositive. The commonest AxSpA-PsO diseases included PsO (N = 1232, 24.8%), PsA (N = 1116, 22.5%) and AxSpA (N = 467, 9.4%). SLE was the commonest SARD (N = 376, 7.6%), a third (N = 133, 35.4%) reported previous lupus nephritis. 1241 (25.0%) patients reported >1 IMID diagnoses. The commonest overlaps were PsO and RA (N = 108, 2.2%), PsO and AxSpA (N = 72, 1.5%) and RA and Sjögren’s syndrome (N = 65, 1.3%). 2880 (58.0%) reported minimum one (range 1-11) co-morbidity, the commonest, hypertension (N = 1201, 24.2%), depression (N = 820, 16.5%) and asthma (N = 580, 11.7%). 274 (5.5%) patients reported ischaemic heart disease, commonest in RA (N = 152, 6.2%). Interstitial lung disease was reported by 75 (1.5%) patients, again most frequent in RA (N = 48, 1.9%). Overall, 696 (14.0%) IMID patients had ≥3 co-morbidities. Oral steroid use was highest in SARD (N = 166, 34.7%). The commonest DMARD in all groups was methotrexate, followed by sulfasalazine in RA (N = 379, 15.3%) and AxSpA-PsO (N = 189, 9.4%) and mycophenolate mofetil in SARDs (N = 69, 14.4%). Overall, 2079 (41.9%) IMID patients were receiving a biological DMARD. Conclusion A high proportion of IMID patients have more than one IMID diagnoses. Significant multi-morbidity with cardiovascular, respiratory and mood disorders was observed and considerable ongoing glucocorticoid usage. The IMID-Bioresource aims to refine patient subsets based on shared immune mechanisms to ultimately, improve precision medicine and patient outcomes. Disclosure S. Dyball: Grants/research support; MRC. Other; GSK, UCB. E. Vital: None. S. Plein: None. D. McGonagle: None. A.G. Pratt: None. J. Isaacs: None. B. Griffiths: None. W. Ng: None. J. McBeth: None. C.E.M. Griffiths: None. B. Parker: Honoraria; Fresenius-Kabi, AbbVie. Grants/research support; GSK, Genzyme/Sanofi. Other; Eli Lilly, Roche. M.H. Buch: None. I. Bruce: Consultancies; ILTOO, AstraZeneca, Eli Lilly, GSK, Merck Serono, UCB. Grants/research support; Genzyme/Sanofi, GSK, UCB, Roche. Other; AstraZeneca, GSK, UCB.