This prospective double blind trial compares the clinical findings of Swanson and Neuflex metacarpophalangeal joint replacements in patients with rheumatoid arthritis, up to 2 years follow-up. There were 37 joints (10 patients) in the Swanson group and 40 joints (12 patients) in the Neuflex group. Assessments of range of movement, grip strength and hand function were undertaken in a double blind fashion, pre-operatively and up to 2 years following implantation. The mean and standard deviation of the data were calculated. A two-tailed student's t-test was used when comparing groups of data. An X-ray analysis was also undertaken to identify any implant failure. There was no significant difference between the two groups with respect to flexion and extension before surgery. At follow-up there was also no significant difference in the extensor lag, with mean extension lags of 19 degrees and 16 degrees for the Swanson and Neuflex implants, respectively. However, there was a significant difference in flexion, with mean active flexion values of 59 degrees and 72 degrees for the Swanson and Neuflex implants, respectively. There were no differences between the two groups in respect to arc of metacarpophalangeal joint motion, ulnar deviation, grip strength or the SODA function test at follow-up. At this early stage there was no evidence of any case of implant failure. In conclusion, patients who underwent Neuflex metacarpophalangeal joint replacements obtained greater flexion than those who underwent a Swanson replacement.