We conducted a study to identify socioeconomic factors associated with unconstrained growth among preschoolers in Muscat, Oman. A sample of children born in 1995 and aged 28-43 months was drawn from the Child Health Registers of 2 health care centres. Sociodemographic data were collected by oral interview and maternal and child anthropometry measured. Regression analysis was used to identify socioeconomic indicators and cut-offs associated with unconstrained growth. Children from households with a monthly income > or = 800 Omani rials and mother's education > or = 4 years attained height-for-age levels comparable to the current international growth reference. By screening using this criterion, we could obtain a suitable sample for the World Health Organization Multicentre Growth Reference Study in Muscat.