[en] Ra-226 started to be used in Spain in the decade of the twenties. During several decades, before the regulatory control was established, a number of users, mainly radiologists practising radiotherapy, gynaecologists and dermatologists, imported a large number of Ra-226 sources into the country. Once the regulatory authority was established, the reconstruction of the source inventory was initiated. With the support of the General Direction of Health, and of commercial enterprises a list of possible owners of Ra-226 was obtained. The list included 175 persons or companies and a total activity of about 20 Ci. A campaign for location of the sources was initiated in the different provinces; the campaign involved contacts with the College of Physicians, as well as Radiological, Radiotherapeutic, Dermatological and Gynaecological Societies, as a result, a total of 3,101 sources with a total activity of 15 Ci were located, retrieved and safely stored; therefore, about 5 Ci remain still to be located; moreover, since the list might only account for about 80% of the actual sources, there is still a significant number of sources missing. In 20 cases leakage of the sources was found, in two of them there was a large contamination requiring significant decontamination actions. The campaign continues up to present; the difficulties in tracing the sources increase with time, due to death of possible Ra-226 owners and relatives. (author)