This paper presents a detailed analysis of waterfalls and culverts as physical barriers to upstream migration by salmon and trout. Analysis techniques are based on combining barrier geometry and stream hydrology to define the existing hydraulic conditions within the barrier. These conditions then can be compared to known fish capabilities to determine fish passage success. A systematic classification system is developed which defines the geometric and hydraulic parameters for a given stream discharge. This classification system is organized in a format that can be used to catalog barriers in fisheries enhancement programs. The analysis compares hydraulic conditions and fish capabilities in detail, as the fish enters the barrier, attempts passage and exits the barrier. From this comparison the parameters which prohibit passage can be determined. Hydraulic conditions are a function of the barrier geometry and stream hydrology, and the stream flow is constant at the time each step in analysis is performed. Therefore, the barrier geometry must be modified to alter the hydraulics to meet fish capabilities. Modifications can be accomplished by: installing instream 'control' structures which deflect the flow or raise pool levels; blasting to alter or remove rock; and installing a fishway to bypass the barrier. Modifications should not be attempted until the analysis defines the excessive parameters which should be modified.