['To study further the temporal clustering of ankylosing enthesopathy (AE) noted originally during a study of the influence of mouse major histocompatibility complex (MHC) H-2 and transgenic HLA-B27 on the frequency of AE.', 'The relationship between maternal age at littering and frequency of AE was analysed.', 'Mice born to mothers aged eight months or older had a significantly lower disease frequency of AE than mice born to mothers younger than eight months of age. This phenomenon was observed in three independent cohorts evaluated to date (p < 0.01, 0.025, and 0.05).'] Does maternal age influence risk for HLA-B27 associated ankylosing enthesopathy in transgenic mice?