This essay highlights the necessity for the establishment of new instream flow standards, as well as the revision of existing standards. This presents a problem since the standards themselves cannot be defined scientifically. The authors recommend the implementation of an adaptive management program involving three elements; setting conservative interim standards; establishment of an adequate monitoring program involving active manipulation flows; and establishment of effective procedure to revise the interim standards. The program details should vary from case to case, especially for species like salmon, where adult populations depend on a myriad of factors, not simply instream flows. Examples of current and previous uses of these standards are given.