At a time of controversy about the appropriate use of obstetric ultrasound, this study explores the effect of availability on ultrasound use. Using a historical cohort design with chart review, pregnancy ultrasound rates were compared between two teaching family-medical centres, one with on-site ultrasound facilities and one without. Pregnant patients at the centre with on-site facilities (n=23) were 2.2 times more likely (p<0.05) to have an ultrasound scan than patients (n=20) cared for at the centre without facilities. At both centres, patients who had one ultrasound scan stood a 50% chance of having another. The implications for family medicine training are discussed.