The river rises to the east of Salisbury near Clarendon Park, where it has been dammed to form a lake. It flows south towards West Grimstead, then turns east and crosses the county border into Hampshire as it passes between the villages of West Dean and East Dean. After passing north of Lockerley and Dunbridge, it joins the Test near Kimbridge. The Test ultimately drains into Southampton Water.
The valley is followed by the Southampton to Salisbury railway and bore the route of the Salisbury and Southampton Canal between Kimbridge and East Grimstead, marked as (the) Old/old canal on many modern maps.