A sample of 100 first graders participated in a study of the relationship between three types of spacing used in written sentences for segmenting word boundaries and pupil errors in completing word-boundary tasks. The results indicated that eliminating printer's word boundaries in written sentences had a significant effect on first graders' performance. In this investigation, there were more total errors on sentences with no boundaries between words. The second most frequent number of errors occurred for sentences with a boundary after every other letter. The fewest number of errors occurred for sentences with printer's word boundaries. Major types of errors associated with word-boundary tasks are also discussed. (AA)