OBJECTIVE Secondary hyperparathyroidism may cause bone loss and structural deterioration of bone and may thus be a cause of fracture in the elderly. Vitamin D deficiency, renal impairment and medications are potential causes of hyperparathyroidism and may also directly predispose to fracture. We present the first findings of an ongoing study of hip fracture, vitamin D deficiency and hyperparathyroidism in a large Australian nursing home.DESIGN Descriptive prevalence study.PATIENTS Two hundred and fifty‐one nursing home residents were eligible for inclusion. Informed consent and successful venepuncture were obtained for 99. Residents were of median age 83 years with interquartile range (IR) 77–89 years.MEASUREMENTS 25‐Hydroxyvitamin D (25OHD), intact parathyroid hormone (PTH), creatinine and biochemistry, demographic data and current medications.RESULTS Fifty‐two per cent of 99 subjects had 25OHD below the reference range of 28–165 nmol/l and 96.5% were below the reference range mean. Those with low 25OHD had lower plasma calcium corrected for albumin than those with normal 25OHD (medians 2.34vs2.41mmol/l, 95% confidence interval for the difference between medians (CI) −0.10 to −0.04 mmol/l,P=0.0001) and higher PTH (medians 5.8vs3.9 pmol/l, CI 0.10–2.6pmol/l,P=0.0360). Twenty‐eight per cent of 97 residents had PTH above the upper reference range limit of 6.5 pmol/l. Residents receiving frusemide had higher PTH than other residents (medians 6.95vs3.45 pmol/l, CI 1.9–4.2pmol/l,P<0.0001). In linear modelling, the most important predictor of the natural logarithm of PTH was daily frusemide dose, adjustedR2(Ra2)=31.8%,F=39.3,P<0.001. Creatinine and the reciprocal of 25OHD were other significant predictors with the finalRa2=39.4%,F=17.7,P<0.001.CONCLUSIONS Vitamin D deficiency is a common risk factor for secondary hyperparathyroidism in nursing home residents despite a climate in which vitamin D nutrition is thought to be ample. However, the daily frusemide dose is a more impo