Although the Autobiographical Memory Test (AMT) is widely used its psychometric properties have rarely been investigated. This paper utilises data gathered from a 10-item written version of the AMT, completed by 5792 adolescents participating in the Avon Longitudinal Study of Parents and Children, to examine the psychometric properties of the measure. The results show that the scale derived from responses to the AMT operates well over a wide range of scores, consistent with the aim of deriving a continuous measure of over-general memory. There was strong evidence of group differences in terms of gender, low negative mood, and IQ, and these were in agreement when comparing an item response theory (IRT) approach with that based on a sum score. One advantage of the IRT model is the ability to assess and consequently allow for differential item functioning. This additional analysis showed evidence of response bias for both gender and mood, resulting in attenuation in the mean differences in AMT across these groups. Implications of the findings for the use of the AMT measure in different samples are discussed.