This study was carried out in 75 patients with histologically confirmed breast cancer. Patients were divided into three groups of 25. The control group received symptomatic corrective therapy prior to mastectomy. The two other groups were given neoadjuvant therapy with Ukrain injections. The first group received a total course dose of 50 mg Ukrain at single doses of 5 mg injected every second day (a total of 10 injections) and the second group received a total Ukrain dose of 100 mg but with single doses of 10 mg. Five to seven days after the last injection patients from all groups were subjected to mastectomy according to Halsted, Patey or Madden. No allergic reactions or adverse effects were observed after the first course of injections or the whole course of Ukrain therapy, regardless of the dose. After five to six injections some patients noticed slight burning sensations and insignificant morbidity in the tumor area, which, according to a number of authors, testifies to the therapeutic activity of the preparation. Practically all patients who were administered Ukrain noticed remarkable positive changes in the second half of treatment: improvement in appetite, normalization of sleep, disappearance of general weakness and the appearance of confidence in recovery. After the course of treatment with Ukrain, the contours of the tumorous node became more clearly defined, which facilitated mastectomy. Changes in the tumor tissue were one-sided in their qualitative differences in comparison to the control group and were not dose-dependent. Qualitative and quantitative reactions to Ukrain by both intact lymphatic nodes and those affected by the metastatic process contribute to more quantitative and radical performance of the most important stage of mastectomy--removal of the regional cellulose together with the lymphatic nodes. The results of this study showed the efficiency of both doses (50 and 100 mg) of Ukrain with neither performing significantly better than the other.