The basic idea behind the Modular Stepwise Procedure is to conduct stream assessments that involve various specialist disciplines and are suitable for projects on different scales. The module in question presents a methodical basis for assessing wadeable Swiss streams using fish as indicators. The scale of the survey and the input of resources are geared towards assessments conducted at the regional level. Using fewer meaningful parameters, a rough assessment is made of fish ecology in selected, representative experimental stretches. The variations in the parameters are evaluated using a points system and the relevant section of water is finally assigned to one of five different categories. The results indicate where action needs to be taken from a fishfauna standpoint.