This comparative prospective study elucidates whether breast reconstruction that is not associated with systemic oncological treatment may trigger a tumour relapse, and if there is any difference between the evaluated reconstruction methods, a simple procedure using an implant versus a TRAM flap, on this hypothetical influence. The study group of 95 patients suffered from stage I-II of breast carcinoma. As regards the available reconstruction procedures, the study group was divided into two subgroups, the first using an implant (n1 = 33) and the second using a TRAM flap (n2 = 62). All oncological problems manifesting during the subsequent 12 months were considered as a response to the reconstruction. The oncological course was compared with two control groups. The first control group (k1 = 82) corresponded to the study group in terms of tumour stage (I-II), average age, time of initial diagnosis, type of primary surgery, i.e. mastectomy with axilla exenteration, and subsequent oncological treatment. The second control group (k2 = 19,625) was based on the National Oncology Register data. It was formed from all patients with breast carcinoma stage I-II from 1985-1994. The disease development in terms of the relative number of relapses and deaths was compared to the number of healthy and living patients, respectively, in the preceding year. The working hypothesis of late breast reconstruction (i.e. not associated with oncological treatment) being a possible trigger effect on the subsequent course of breast cancer has not been confirmed. No statistically significant differences at the 5% significance level were found between individual reconstruction methods and control groups in terms of the number of local relapses and survival length.