Summary. Thirty‐six women with dyskaryotic cervical smears and unsatisfactory colposcopy were randomly allocated to receive either 30 μg ethinyl oestradiol or placebo daily by mouth for 10 days. Thirty‐four women were available for review (17 women in each of the two groups), full colposcopic inspection of the transformation zone was possible in a significantly greater proportion of the oestrogen treated group (70% versus 23%, P<0.01). As most diagnostic conizations are currently performed on the basis of unsatisfactory colposcopy, the use of oestrogen medication followed by colposcopic reassessment should permit a reduction in the number of patients subject to operation.