To examine the relationship between albuminuria and measures of body morphology. Cross-sectional study of European, Maori and Pacific Island workers aged 40 y and over. 3960 non-diabetic, non-hypertensive, non-lipidaemic, non-proteinuric middle-aged men and women. Height, weight, waist, hip, fasting and 2 h glucose, systolic and diastolic blood pressure, urinary creatinine and urinary albumin measurements. After adjusting for age and gender, the relative risks (95% confidence interval) of microalbuminuria were 4.87-fold (3.10-7.64) higher in Maori, and 4.96-fold (3.40-7.24) higher in Pacific Islanders compared to European New Zealanders. In contrast, age and gender adjusted relative risks (95% confidence interval) for high albumin:creatinine ratios were 6.38 (4.27, 9.53) in Maori and 5.14 (3.54, 7.48) in Pacific Islanders compared to European workers. Workers with microalbuminuria had higher urinary creatinine concentrations than those with urinary albumin in the normal range. Age and gender adjusted partial correlation coefficients between urinary albumin concentrations and the inverse of urinary creatinine concentrations were highest in European and Maori workers. Apart from Pacific islanders, urinary creatinine concentrations accounted for over 20% of the variation in urinary albumin concentrations in healthy individuals. Other independent predictors of urinary albumin concentrations were waist measurements, short stature and body mass index in Europeans and Pacific Islanders, and systolic blood pressure levels and gender in Europeans. After adjusting for age, gender, waist, height, 2 h glucose, urinary creatinine, systolic blood pressure and body mass index Maori and Pacific Islanders still had significantly higher urinary albumin concentrations than Europeans. Urinary creatinine concentrations were significantly associated with urinary albumin concentrations in all ethnic groups, and, with the exception of Pacific Islanders, accounted for a large proportion of the variation in urinary albumin concentrations in healthy individuals. Urinary albumin concentrations were associated with measures of obesity and short stature in Europeans and Pacific Islanders, and systolic blood pressure levels and gender in Europeans. However, measures of body morphology did not completely explain the higher urinary albumin concentrations in Maori or Pacific Islanders.