The S-R Inventory of Anxiousness was developed as an experimental design to demonstrate the relative contributions of persons, situations, modes of response, and their interactions to individual differences in anxiety. College students in three studies were asked to rate a total of 154 items, involving 14 modes of response (physiological or overt behavioral indicators) and eleven anxiety-arousing experiences. Three major problems are discussed: (1) the apparent lack of distinction between "person" and "mode of response"; (2) influence of the non-random selection of "situations" and "mode of response" on the results of the analysis; and (3) problems in specifying and assessing the nature of person-situation interactions. While initial efforts to statistically demonstrate variance contribution of interactions deserve recognition, the variance components approach and previous application of the S-R Inventory do not lead to clarifying the specific nature of person-situation interactions in influencing anxiousness. Future research on person-situation interactions, therefore, identify specific person and situation characteristics and incorporate aspects of both these factors in a systematic research design. (Author/CP)