findings could have been due to bias. The World Health Organisation is studying the risk of cancer in women using medroxyprogesterone at centres in Thailand, Kenya, and Mexico.' The most recent report from this case-control study (based on 39 cases who had used medroxyprogesterone) yielded a relative risk for all women using the drug of 1-0 (95% confidence interval 0-7 to 1 5).3 Relative risks were not shown separately for women diagnosed as having breast cancer before age 35, for women who used the drug before age 25, or for women who reported using it recently; it will be important to see whether more detailed analyses replicate our findings and, if so, which of these groups are specifically at risk.If our results are confirmed the indications for using medroxyprogesterone will need to be reassessed. The findings will also contribute to discussions about the relevance of the beagle model and about the pathogenesis of breast cancer.

The prevalence of recognised urinary incontinence in a community was found to be 1%; the prevalence of unrecognised incontinence was 3.3% in men and 8% in women in a group practice of 7000 patients. The approach to investigation and management of urinary incontinence in a urodynamic unit and the staffing of this unit are described.

upon Tyne NE2 4HH1 The inhibitory transmission in isolated preparations of cavernosal smooth muscle from human penis has been studied. 2 Electrical field stimulation (EFS; 2-64 pulses/train, 0.8 ms pulse duration, 10Hz) evoked relaxation of preparations treated with guanethidine (5OpM). The EFS-evoked relaxations were atropine-resistant and tetrodotoxin-sensitive indicating their origin to be non-adrenergic, non-cholinergic (NANC) nerve stimulation. 3 EFS-evoked relaxation was attenuated dose-dependently by the nitric oxide (NO)-synthase inhibitor, L-NG-nitro arginine (L-NOARG; 0.3-100,aM) but not by D-N0-nitro arginine. The inhibitory effect of L-NOARG on transmission was antagonized by L-arginine (100pM), a NO precursor, but not by D-arginine.4 Incubation with methylene blue (10-50pM), a known inhibitor of guanylate cyclase activation by NO, caused a concentration-related inhibition of EFS-evoked relaxation. 5 It is concluded that NANC nerve-evoked relaxation of human cavernosal smooth muscle is mediated by NO or a NO-like substance.

Impotence may be caused by arterial disease affecting the vessels supplying the corpora cavernosa. Color duplex ultrasound was used to measure the peak systolic velocity and systolic rise time in the deep penile arteries in 22 impotent men following papaverine stimulation. The results were compared with the findings of selective internal pudendal pharmaco-arteriography. A further comparison was made using color duplex ultrasound with 37 impotent men who all responded well to papaverine. A systolic rise time of 110 msec. or more was found to be the best discriminant of disease in the arteries supplying the corpora giving a positive predictive value of 0.92. A long systolic rise time in a papaverine responder may indicate that the arterial supply is borderline or that the arterial flow is maximal and that the problem lies on the sinusoidal-venous side. It appears that in the absence of a pathological condition there is a large surplus arterial supply.

The results of testing posterior urethral electrosensitivity in a variety of urological conditions are demonstrated and the relationship between urethral sensitivity and the standard urodynamic investigations discussed. The clinical features of a group of patients with urethral hyposensitivity are presented.