This chapter is one of the intermittent series which has had "assess ment" in its title. The authors have dropped that term because of its impre cision and its connotations. Assessment has often been used to refer to the combining of measures, usually by human judgment, to predict a criterion. But personality measurement as a whole involves the combination or reduc tion of observations to obtain an index and is concerned with much more than the prediction of criteria. Additionally, the terms assessment and crite ria have an evaluative flavor; while adequacy of functioning is involved in much of personality, a science of personality must not be limited to norma tive considerations. Finally, assessment has the connotation of dealing with the whole person. It seems quite clear that we cannot have a science of the whole person, or even of substantial segments of personality, until we un derstand the components.Most concepts in the personality field are so broad and heterogeneous in their referents that when one concept is used to describe different persons, it is very doubtful that the identical attribute is applied to each. The task fac ing personality today is the identifi cation and delineation of attributes which can be uniformly applied to persons, the objects of this science, with the specifi c applications of each attribute differing only in quantity, not quality. Coordinate with that task is the work of developing operations for measur ing each of these attributes. Such procedures must be standardized so that the measurements can, in principle, be replicated for the same persons and, particularly critical in this area, so that the measurements are getting at the same attribute in the different persons measured, without any sizable per son-instrument interaction. This chapter is concerned with the extent to which these standards are being approximated in personality measurement today.A science develops by an interactive or cyclical process, observations leading to concepts, and concepts guiding the next set of observations. In personality, an infi nity of observations has been conceptualized in a variety of sets of terms with general statements about them. These literary or even