| 53698 | Sode S.A. | 3 | 1969 | 1973 |
| 43555 | Sorotxikiko bizilagunak | 1 | 1971 | 1971 |
| 46061 | Stitou Messaud | 1 | 1993 | 1993 |
| 42343 | Suministros para Fundición | 1 | 1974 | 1974 |
| 48242 | Talleres Aduna | 1 | 1955 | 1955 |
| 42342 | Talleres Biyona | 1 | 1974 | 1974 |
| 43416 | Talleres José Mª Elosegi Arregi | 1 | 1961 | 1961 |
| 43494 | Talleres Luis Mª Aya | 1 | 1966 | 1966 |
| 42392 | Talleres Vicuña S.A | 3 | 1965 | 1970 |
| 42462 | Telefonica S.A | 2 | 1971 | 1973 |
| 42514 | Teodoro Usandizaga Beobide | 2 | 1971 | 1972 |
| 52807 | Teresa Aialde | 1 | 1725 | 1725 |
| 52309 | Teresa Altuna | 1 | 1625 | 1625 |
| 52633 | Teresa Arralde | 1 | 1739 | 1739 |
| 52556 | Teresa Elgarresta | 1 | 1759 | 1759 |
| 52954 | Teresa Idiakez | 1 | 1694 | 1694 |
| 48280 | Teresa Mendibil | 1 | 1956 | 1956 |
| 53171 | Teresa Ugarte | 1 | 1714 | 1714 |
| 51740 | Teresa Urruzola | 3 | 1737 | 1739 |
| 52115 | Teresa Usobiaga | 1 | 1783 | 1783 |
| 52940 | Tiburcio Bergara | 1 | 1690 | 1690 |
| 53019 | Tolosako San Frantzisko komentua | 2 | 1699 | 1741 |
| 53085 | Tolosako Santa Klara komentua | 2 | 1692 | 1708 |
| 43089 | Tomar Arrastoa Iguaran | 1 | 1960 | 1960 |
| 52267 | Tomas Aialde Zulaika | 1 | 1659 | 1659 |
| 48285 | Tomas Arrastoa | 1 | 1957 | 1957 |
| 52572 | Tomás Arruebarrena | 1 | 1779 | 1779 |
| 52834 | Tomás Eizmendi | 1 | 1721 | 1721 |
| 47454 | Tomas Fagoaga Rementeritegi | 1 | 1652 | 1652 |
| 48278 | Tomas Garikano Goñi | 1 | 1956 | 1956 |
| 42966 | Tomas Irazu Amondarain | 1 | 1965 | 1965 |
| 52167 | Tomás Maiz | 1 | 1734 | 1734 |
| 52466 | Tomás Muñoa | 1 | 1821 | 1821 |
| 42515 | Tomas Otamendi Arratibel | 2 | 1973 | 1973 |
| 48136 | Tomas Urdapilleta | 1 | 1752 | 1752 |
| 51982 | Tristan Lizarraga | 2 | 1653 | 1758 |
| 42969 | Txapartegi Hermanos | 1 | 1965 | 1965 |
| 49791 | Txomin Otegi Aldai | 1 | 2004 | 2004 |
| 43541 | Ubar Ingeniariak | 1 | 1968 | 1968 |
| 43018 | Udala | 1 | 1950 | 1950 |
| 42269 | Ugalde Rekondo ahizpak | 1 | 1974 | 1974 |
| 43146 | Urbana Izagirre Segurola | 1 | 1961 | 1961 |
| 42999 | Urbar Ingenieros S.A. | 10 | 1960 | 1973 |
| 51685 | Urnieta | 1 | 1694 | 1694 |
| 53158 | Úrsula Lizaristi | 1 | 1713 | 1713 |
| 52350 | Úrsula Otamendi | 1 | 1700 | 1700 |
| 42476 | Valentin Mayoz Iraola | 2 | 1958 | 1969 |
| 42561 | Venancio Segurola | 2 | 1969 | 1974 |
| 42448 | Venancio Segurola Iraola | 4 | 1965 | 1974 |
| 52057 | Vicenta Olaskoaga | 1 | 1721 | 1721 |
