Primary total hip arthroplasties have reported success rates of greater than 95% in many series with a longer than 10-year follow-up. Revision total hip arthroplasty due to such factors as increased high-activity levels, younger patients undergoing the procedure and increasing life expectancy has become more prevalent. An understanding of the mechanisms and timing of total hip arthroplasty failure can direct efforts aimed at reducing revision rates. This study was conducted to evaluate the indications for revision hip arthroplasty and relate these to the time after the index primary hip arthroplasty. A review of all revision hip arthroplasties at two centres over a 6-year time period identified 225 patients who underwent 237 revisions. The overall mean time to revision was 83 months (range: 0-360 months). The cause of failure was aseptic loosening in 123 hips (51.9%), instability in 40 hips (16.9%) and infection in 37 hips (5.5%). When stratified into two groups (less than 5 years, more than 5 years after the index primary hip arthroplasty), 118 of 237 (50%) revisions occurred in less than 5 years, with 33% due to instability and 24% resulting from infection. The majority of the causes of failure within 5 years in these early revisions were instability and deep infection. The success of hip arthroplasty is likely to be compromized if technical aspects of the surgery for appropriate component positioning and critical protocols to minimise complications such as infection are not given the proper attention.