The Social Phobia Scale (SPS) and the Social Interaction Anxiety Scale (SIAS) were developed as a companion set of measures by Mattick and Clarke in 1998. The scales correlated well with established measures of social anxiety, but were found to have low or non-significant (partial) correlations with established measures of depression, state and trait anxiety, locus of control, and social desirability. The scales were found to change with treatment and to remain stable in the face of no-treatment. It appears that these scales are valid, useful, and easily scored measures for clinical and research applications.