To identify variables affecting length of hospital stay after total hip replacement (THR) while controlling for potential confounders. Records of 199 consecutive elective unilateral THRs were reviewed. Clinical and demographic data including age, gender, body mass index, comorbidities, surgical factors (surgical approach, type of prosthesis, use of cement, operating time), anaesthetic factors (type of anaesthesia, ASA physical status), and length of hospital stay were recorded. 64% of patients left hospital within 12 days, 28% within 3 weeks, and 8% after 3 weeks. The median length of hospital stay was longer in women than men (11.5 vs. 9 days, p=0.009), in patients aged >65 years than those younger (13 vs. 9 days, p<0.0001), and in those with American Society of Anesthesiologists (ASA) grades 3 and 4 than grades 1 or 2 (14 vs. 9 days, p<0.0001). A greater proportion of women than men (45% vs. 27%, p=0.007), patients aged >65 years than those younger (61% vs. 37% or 24%, p<0.0001), and those with ASA grades 3 and 4 than grades 1 and 2 (68% vs. 25%, p<0.0001) stayed 12 days or longer. In the multiple regression analysis, the predictors for prolonged hospital stay (12 days or more) were patient age >65 years (p<0.003), female gender (p<0.05), and ASA grades 3 and 4 (p<0.0001). Of the 72 patients with prolonged stay, 7% had no, 26% had one, 42% had 2, and 25% had all 3 predictors. Prolonged hospital stay after THR is largely predetermined by case mix. Our study helps to identify individuals who need longer rehabilitation and more care.