Introduction: Primary Mesangial Nephropathy (PMN) is an heterogeneous set of pathologies characterized by the expansion of the extracellular matrix, mesangial deposits -frequently of IgA or IgM, associated or not to hypercellularity. Objectives: Our objectives were to establish the prevalence of PMN at the Hospital Militar Central, determine demographic and epidemiologic characteristics, and evolution. Methods: Observational retrospective study. Medical records and kidney biopsy reports have been reviewed. Laboratory data were obtained, consultation dates were recorded, as well as onset of symptoms, remission of proteinuria, and therapy. Results: Out of 106 biopsies, 24 (20.2%) were PMN, 20 IgA, and 4 IgM. They presented isolated abnormalities of the urine sediment (52.2%), nephrotic syndrome (26.1 %), and nephritic syndrome (21.7%). Twenty-one patients received renin-angiotensin system receptor blockers, 12 received immunosuppression. Baseline proteinuria was 2.93 (±2.10) gr/d, one year later: 0.95 ±2.1 gr/d (p: 0.06), two years ter: 0.55 ±0.7 gr/d (p: 0.03). They had full remission (50%), full relapse (25%), partial remission (20%), and no remission (5%). Time until remission: 355.39 days (CI: 101-610). Patients with proteinuria lower than 1gr/d: full remission (29%), remission-relapse (57%), partial remission (14%). With proteinuria higher than 1gr/d: full remission (64%), remission-relapse (9%), partial remission (18%), no remission (9%). Follow-up time: 79.92 ± 87.9 months. Eight patients were followed up for 5 years, baseline creatinine 1.13± 0.4, final 1.58 ±1.1 mg/dL (p=0.67). Baseline urinary protein of 2.93±2.8 gr/d, and final value of 0.77±0.88 gr/d, (p=0.069). One patient required transient dialysis, another one required chronic dialysis and died. Conclusions: PMN is the first biopsied renal pathology. Urinary protein decreased considerably. Patients with urinary protein over 1gr had higher remission and lower relapse; creatinine showed an upward tendency that was not significant.