The purpose of this study was to examine expert and novice volleyball coaches' diagnostic ability of a volleyball skill. Specifically, this study investigated the differences between expert and novice volleyball coaches in a) knowledge base of the volleyball spike, b) information cue acquisition and interpretation, c) linkage between knowledge structure and diagnostic performance, and d) the diagnostic decisions regarding coaches' corrective recommendations for performance improvement. Four expert and four novice Iowa high school volleyball coaches participated in this study. Research procedures included an interview regarding an ideal volleyball spike, a recall test on slides of volleyball spiking images, and a diagnostic task where the coaches analyzed the volleyball spike performance. Data analysis revealed differences of coaches' diagnostic ability between expert and novice volleyball coaches. Expert coaches' knowledge regarding the volleyball spike was richer and more extensive than that of novices in a) the number of the components identified, b) the number of body parts used to describe the skill, and c) in the judgment as to which issues are most critical in skill execution. Expert coaches' explanations about an ideal spike demonstrated the knowledge that was more technically specific, and procedure-oriented, which may have been enhanced by their years of successful coaching experience. Interpretation of acquired cues differed between expert and novice coaches in this study. Expert coaches' recall statements were more evaluative and technique-related. Novice coaches, on the other hand, were more descriptive and game-situation oriented. Although both expert and novice coaches perceived a similar number of information cues during the skill diagnosis, experts perceived a greater number of information cues in technique deficiencies as compared to the novices, specifically in the approach and the jump phases. The results revealed connections between coaches' knowledge of the volleyball spike and their diagnostic performance. It appeared that coaches' diagnostic ability depends on the schemas pertaining to an ideal volleyball technique and its critical features. Expert coaches' recommendations for skill improvement were based on more extensive analysis and reasoning. Their suggestions were more sequential and process- based than the novice coaches.