Patients with Down's syndrome (DS) have an increased incidence of coxarthrosis which may become symptomatic with prolonged life expectancy. We present seven consecutive patients (nine hips) with DS who had primary total hip arthroplasty (THA). Average clinical and radiological follow-up was 9.9 ± 6.4 years (range 2-22.25). Harris hip scores (HHS) improved significantly (p < 0.01) from 41.1 (range 18.5-65) to 80.2 (range 67.5-91) at latest follow-up. Two patients required revision arthroplasty for stem loosening at 16 (osteolysis) and six years (trauma) following THA, respectively. Six of the THAs required a constrained liner. No dislocations or deep infections were encountered. We contend that THA is a reliable surgical intervention in patients with DS and may be performed in symptomatic patients.