Few instruments have been developed for evaluation of expressive vocabulary in early childhood. This project attempted to develop an instrument sufficiently structured to call forth appropriate verbalization yet varied enough to elicit a wide range of responses, and to use the instrument to test whether socioeconomic class groupings can be differentiated by the quantity and quality of the child's verbal output. The Expressive Vocabulary Inventory (EVI), the instrument developed, consists of 40 items in which the child is shown a line-drawing and asked a question to which he answers the appropriate word or phrase. The EVI was given to 204 boys and 226 girls (145 Caucasian and 285 Negro, 300 low and 130 high socioeconomic status categories) in three age groups (36-47 months, 48-59 months, and 60-71 months). No statistically significant differences for sex were obtained within any of the age groups. Some support for a cumulative decrement could be seen by comparing the difference at age 3 with that at age 5, but the small number of 5-year- old children confounded the expected decrement with increase in age for the lower economic status children. (Directions for administering the EVI and sample items are appended.) (LH)