An anti-RORl antibody or antigen-binding fragment, comprising a heavy chain variable (V H) region comprising a heavy chain complementarity determining region 1 (CDR-H1), CDR-H2, and CDR-H3, and a light chain variable(V L) region comprising a CDR-L1, CDR-L2, and CDR-L3, wherein: the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 20, 21, and 22, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 23, 24, and 25, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 20, 26, and 22, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 23, 24, and 25, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 218, 229, and 39, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 30, 31, and 32, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 216, 227, and 40, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 217, 228, and 41, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 212, 223, and 42, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 36, 37, and 38, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 219, 230, and 43, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 215, 226, and 44, respectively; and the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 164 and 45, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 220, 231, and 46, respectively, wherein the antibody or fragment is human; and wherein the antibody or fragment competes for binding to a human ROR1 protein with anti-RORl antibody R12 or an antigen-binding fragment thereof, which is optionally an scFv fragment of R12. the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 20, 21, and 22, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 23, 24, and 25, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 20, 26, and 22, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 23, 24, and 25, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 218, 229, and 39, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 30, 31, and 32, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 216, 227, and 40, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 217, 228, and 41, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 212, 223, and 42, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 36, 37, and 38, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 28, and 29, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 219, 230, and 43, respectively; the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 33, 34, and 35, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 215, 226, and 44, respectively; and the CDR-H1, CDR-H2, and CDR-H3 comprise the sequences of SEQ ID NOs: 27, 164 and 45, respectively, and the CDR-L1, CDR-L2, and CDR-L3 comprise the sequences of SEQ ID Nos: 220, 231, and 46, respectively, wherein the antibody or fragment is human; and wherein the antibody or fragment competes for binding to a human ROR1 protein with anti-RORl antibody R12 or an antigen-binding fragment thereof, which is optionally an scFv fragment of R12.