Methods and compositions for use in modulating the activity(s) of WISP-1polypeptide are provided. WISP-1 antagonists include anti-WISP-1 antibodies,WISP-1 immunoadhesins and WISP-1 variants (and fusion proteins thereof) whichinhibit or neutralize induction or secretion of HAS2, HA, CD44 or RHAMM bynative human WISP-1 polypeptide in at least one type of mammalian cell. Theinvention also provides methods for in vitro, in situ, and/or in vivodiagnosis and/or treatment of mammalian cells or pathological conditionsassociated with native WISP-1 polypeptides.