Two test devices were manufactured to objectively measure ankle joint laxity: the dynamic anterior ankle tester (DAAT) and the quasi-static anterior ankle tester (QAAT). The primary aim was to analyse the reliability of both testers; The secondary aim was to assess validity in correlation with TELOS stress test and manual anterior drawer test. Twenty-four normal subjects and 14 patients 1 year after acute lateral ankle ligament injury were included. Both ankles were tested with the DAAT and QAAT by two different observers; one experienced orthopaedic surgeon performed the manual test; the TELOS stress X-rays were evaluated by one observer. Intra observer reliability for the DAAT varied between 0.81 and 0.94; for the QAAT between 0.71 and 0.94. Inter observer reliability for the DAAT varied between 0.84 and 0.94; for the QAAT between 0.76 and 0.82. Concurrent validity showed fair correlation between DAAT and QAAT for the first couple observers (0.71); however, a poor correlation was observed for the second couple (0.42). No significant correlations were found between neither DAAT and the TELOS and the manual test, nor QAAT and the TELOS and the manual test. In conclusion, reliability of both testers is high. Validity of the testers needs further investigation.