Two experiments were designed to examine the alpha-numeric category effect in visual search (e.g., Jonides & Gleitman, 1972). In Experiment 1 subjects searched circular stimulus displays for a single target item embedded in a context either or letters or digits. When the field items were letters this target was specified as any digit, or was the character "0" specified as "oh" (same category) or "zero" (different category) . For digit field items the corresponding target conditions were any-letter, same-category (zero) and different- category (oh). The percentage of correctly located targets was recorded, and the accuracy measures obtained when 0 was specified as belonging to the same category as the field items did not differ from the measures obtained when it was specified as belonging to the different category. However, while selection in the letter context was more difficult in the case of the any-digit target than in the case of the 0 targets, performance in the digit context was not influenced by the type of target. It was suggested that these latter findings were probably a result of the small inter-category size difference characteristic of the type face used, that is, the letters were a little wider than the digits. In Experiment 2 accuracy of search was again compared for target conditions any-digit/letter, 0 as oh/zero and 0 as zero/oh, in letter and digit contexts respectively. But, care was taken to select a type face in which letters and digits did not differ in size. The results of the same-category and different-category target conditions replicated those obtained in Experiment l, that is, performance levels did not direr for these conditions. In addition, and in contrast to the finding in the previous study, there were no detectable differences between the obtained accuracy levels in the letter-context and digit-context conditions, and selection of any-digit/letter targets was more difficult than selection of the 0 targets. It was argued that the absence of an alpha-numeric category effect (i.e., performance was not superior for the different-category conditions in the case of the 0 targets), supported the suggestion that initial selection is based on an analysis of physical or formal information (Neisser, 1967). And, it was suggested that it is possible to account for the presence of a category effect in the Jonides and Gleitman study, by considering the delay caused by competing responses during the rejection of incorrectly selected non-targets in the same- category conditions.