Differences in bone mineral density (BMD) patterns have been recently reported between multiple endocrine neoplasia type 1–related primary hyperparathyroidism (HPT/MEN1) and sporadic primary HPT. However, studies on the early and later outcomes of bone/renal complications in HPT/MEN1 are lacking. In this cross-sectional study, performed in a tertiary academic hospital, 36 patients cases with uncontrolled HPT from 8 unrelated MEN1 families underwent dual-energy X-ray absorptiometry (DXA) scanning of the proximal one-third of the distal radius (1/3DR), femoral neck, total hip, and lumbar spine (LS). The mean age of the patients was 38.9 ± 14.5 years. Parathyroid hormone (PTH)/calcium values were mildly elevated despite an overall high percentage of bone demineralization (77.8%). In the younger group (<50 years of age), demineralization in the 1/3DR was more frequent, more severe, and occurred earlier (40%; Z-score −1.81 ± 0.26). The older group (>50 years of age) had a higher frequency of bone demineralization at all sites (p < .005) and a larger number of affected bone sites (p < .0001), and BMD was more severely compromised in the 1/3DR (p = .007) and LS (p = .002). BMD values were lower in symptomatic (88.9%) than in asymptomatic HPT patients (p < .006). Patients with long-standing HPT (>10 years) and gastrinoma/HPT presented significantly lower 1/3DR BMD values. Urolithiasis occurred earlier (<30 years) and more frequently (75%) and was associated with related renal comorbidities (50%) and renal insufficiency in the older group (33%). Bone mineral– and urolithiasis-related renal complications in HPT/MEN1 are early-onset, frequent, extensive, severe, and progressive. These data should be considered in the individualized clinical/surgical management of patients with MEN1-associated HPT. © 2010 American Society for Bone and Mineral Research.