Abstract : Three experiments involving category clustering in lists composed of high-frequency (HF) and low-frequency (LF) associates of the category names are reported. The major results were: 1. Block presentation augments clustering in both lists and augments word recall in HF but not in LF lists. 2. Word recall and clustering are higher in HF lists than in LF lists. 3. Duration of item presentation interval augments both clustering and word recall within limits. 4. An immediate recall augments or maintains clustering and word recall on a second recall, obtained after a short delay. 5. These findings and certain interactions are discussed with respect to the interpretation of recall of categorized lists. It is concluded that a coding hypothesis cannot do justice to all the findings. Associations between the category names and their instances or among the instances themselves are suggested as supplemental or alternative mechanisms. (Author)