The objectives of this research are (i) to describe the medico-administrative characteristics of inpatients aged 65 and more who are hospitalized for hip joint replacement, (ii) to evaluate the complete hospital cost into costs of medical procedures, drugs costs, prostheses costs, and the administrative costs, and (iii) to identify and to evaluate from administrative database predictors influencing the complete hospital costs. The study was based on 961 inpatient stays aged 65 and more, with the APR-DRG 301 "Hip joint replacement". The sample for this study was based on data collected in 2014 among nine Belgian general hospitals. We used the linear regression method for isolating predictors of hospital cost. The study highlights three different types of patients hospitalized for hip replacement, depending on the primary diagnosis: osteoarthritis problems (57%), femur neck fracture (30%), or other reasons (13%) (complications, infections, or problems with the existing hip prosthesis). The median length of stay (P25-P75) was 9days (6.29-20.91). The median cost (P25-P75) was 8,023.91 EUR (6678.32-13,670.78). The total cost was composed of the direct hospital cost (30%), the cost of medical procedures (31%), cost of drugs (4%), the cost of hip prosthesis (18%), and other costs (17%). The linear regression reveals that an extreme SOI or risk of mortality, an ICU stay, an in-hospital death, an index of Charlson comorbidities of 4 or 5, to be hospitalized for a hip replacement because of complications, infections, or problems with the existing hip prosthesis, and the length of stay, were predictors of an increase in hospital cost. The cost is not increasing with the age of the patient, but mainly with the length of stay and the comorbidities linked to the age which are considered in the severity of illness and the Charlson comorbidities index. The hospital cost is higher for patients hospitalized for complications linked to an existing hip prosthesis than for a hip replacement linked to osteoarthritis problems.