Two-stage revision is the most widely accepted and performed intervention for chronically infected hip prostheses. In recent years short and long stem antibiotic-loaded preformed spacers have become available on the market. The aim of this prospective, comparative study was to assess the safety and efficacy of long stem versus short stem preformed spacers. From year 2000 to 2007 102 consecutive patients underwent two-stage revision of septic hip replacement with a preformed antibiotic-loaded cement spacer and a cementless modular hip revision prosthesis. Patients were divided in two groups: Group L (long stem spacer) (N=60) and Group S (short stem) (N=42) and compared. No systemic toxicity due to local antibiotic release and no spacer breakage were observed in either group. At spacer removal, no statistically significant difference was observed in infection recurrence. After revision, at a mean 4 years follow-up, 2 patients in Group L and 2 in Group S showed infection recurrence. The Harris Hip Score improved in both groups, compared to post spacer implant values: 79.6 + or - 15.4 versus 38.4 + or - 14.5 in Group L (p < 0.0001) and 82.3 + or - 14.4 versus 44.8 + or - 16.6 in Group S (p < 0.0001); the difference between groups was not statistically significant. Short and long stem spacers provide comparable low infection recurrence rate and clinical outcome, with negligible risk of breakage and toxicity.