A prospective randomized study was carried out to discover the influence of the timing of shoulder physiotherapy after-axillary dissection for breast cancer upon the incidence and duration of lymphatic fluid production and seroma after these operations. Sixty-eight patients underwent a modified radical mastectomy, 31 were submitted to early physiotherapy and 37 to delayed physiotherapy after removal of the suction drainage. In 32 patients this surgery was conservative of the breast; in 16 the physiotherapy was early and in 16 delayed. The shoulder was left free when the physiotherapy was delayed. The mean volume of lymphatic fluid produced after these 100 axillary dissections was 437 cc (range: 50 to 800 cc) with a mean duration of 6.3 days (range: 2 to 11 days). There was a linear relation between the volume and the duration of the lymphatic fluid production. This volume was significantly higher in radical mastectomy than in conservative procedures (486 cc vs 333 cc - p less than 0.02). There was no significant difference in the production of lymphatic fluid with early or delayed physiotherapy, whatever the group of patients: radical or conservative surgery - age - number of excised lymph nodes - lymph node involvement. Five seromas occurred in patients with delayed physiotherapy. Delaying physiotherapy after axillary dissection for breast cancer does not seem to reduce the incidence of lymphatic complication, but the use of a conservative procedure rather than a modified radical mastectomy seems to be able to do so.