To address the lack of consensus on the leading reasons for readmissions after primary elective unilateral total joint arthroplasties (TJAs), we performed a systematic review and a meta-analysis to identify overall and cause-specific readmission rates. We performed structured searches of the Medline and Cochrane databases for original reports-published between January 1982 and January 2013-on both 30- and 90-day follow-ups of unique patient populations that underwent elective primary TJA. Random-effects meta-analyses were performed to obtain pooled estimates. For total hip arthroplasty (THA), the overall pooled readmission rate was 5.6% at 30 days and 7.7% at 90 days. For total knee arthroplasty (TKA), the overall rate was 3.3% at 30 days and 9.7% at 90 days. The leading reason for THA readmission was joint-specific at both 30 and 90 days, and the leading reason for TKA readmission was surgical site infection. Our systematic review and meta-analysis established baseline readmission rates in the literature on primary TJA and identified the most common reasons driving readmission for TJA.