Synthetic gestagens are substances which can be used for oestrus inhibition or synchronisation after break off in heifers and improvement of fertility. They also increase weight gain and improve feed efficiencies. The test is recommended for the detection of the following gestagens (% of cross-reactivity): medroxyprogesterone acetate (100%), megestrol acetate (50%), melengestrol acetate (25%), chlormadinone acetate (50%). The detection limit of the MPA-EIA kit was found to be 0.5 ng/g for the screening of MPA in kidney fat.