Researchers in speech and language therapy have given too little attention to the basics of clinical outcome research. This requires that clinical and theoretical insights are used to identify specific therapies for well-defined groups of clients. These therapies must be tested first in efficacy, then in effectiveness studies, and their results should be disseminated to clinicians. Only then is it meaningful to carry out large-scale trials of the effectiveness of therapy provision for a client group or to conduct systematic reviews of existing research.