1. 1. Chronic vulval dystrophy is a term used to cover any chronic skin change of uncertain etiology which affects the vulva. It includes not only white lesions sometimes called leukoplakia, kraurosis, and lichen sclerosus, but also red lesions. 2. 2. Multiple vulval biopsy is indicated at the outset of the management of all women with a chronic vulval dystrophy. It aims to detect the presence of cancer or of atypical epithelial hyperplasia which may threaten cancer. 3. 3. The findings in a consecutive series of 294 patients, all of whom had had vulval discomfort for at least one year and who also showed naked-eye vulval skin changes are presented. 4. 4. In 8 cases cancer of some type was found to be present when the patient was first seen. Sixteen women proved to suffer from previously unsuspected diabetes and 9 had well-recognized skin diseases (mostly psoriasis) not specific to the vulva. The last 25 cases were excluded from further consideration. 5. 5. In 82 cases the lesion was essentially red in color, in 109 white, and in 78 partly red and partly white. 6. 6. Cancer was found in 5 red lesions, 2 white ones, and one in which the color was red and white. In one case, carcinoma in situ was found at the age of 23 years and may have been present since the age of 14 years. 7. 7. All patients were investigated for possible etiologic factors which included achlorhydria, deficiency states, monilial vulvitis, fungus infections in other parts of the body (notably the hands and feet), glycosuria, and allergy. 8. 8. Treatment was designed to oppose any possible etiologic factor discovered and, when none was found, fungicides and antihistamines were employed empirically. 9. 9. Partial or total vulvectomy was carried out in only 28 cases, and the dystrophy recurred in more than 50 per cent of these cases. Cancer developed later in one case. 10. 10. Treatment, mostly conservative, was attended by results better than expected. Of 216 women subsequently observed for periods up to 27 years, 82 were cured, 40 cured for intervals between relapses, and 50 improved. 11. 11. Carcinoma of the vulva supervened in only 4 women in this series and that at 7 months, 3 years, 4½ years, and 10 years after the patient was first seen. A fifth case of cancer, developing in a patient not included in this series but previously seen on account of vulval symptoms is mentioned. 12. 12. The likely development of carcinoma is usually foreshadowed by a finding of atypical epithelial activity on biopsy. Such a finding is an indication for vulvectomy although the operation does not necessarily protect the woman from cancer. Otherwise vulvectomy is not recommended as an empirical treatment except occasionally for small clearly circumscribed lesions, when it may be the best form of biopsy. 13. 13. The chance of cancer supervening on a vulval dystrophy within 3 to 25 years is small, not more than 4 to 5 per cent. But even this small risk means that women whose vulval complaint is not completely cured should be kept under observation and subjected to vulval biopsy at intervals if necessary. This is true even if the vulval dystrophy is treated by vulvectomy.