The effects of certain productive and receptive communicative activities on the ability of stutterers and nonstutterers to estimate the passage of time (protensity estimates) were investigated. Three groups of subjects, normal speakers, mild stutterers, and moderate to severe stutterers, were asked to estimate the duration of a ten-second period while engaged in an activity such as: silence, oral reading, silent reading, listening, or spontaneous speech. For the three groups as a whole, the protensity estimates made during silence were significantly more accurate than those during the presence of communicatively oriented competitive stimuli. In addition, the performance of the mildly dysfluent group was closer to that of the normal speaking group than to that of the more severe stutterers. The difficulty in making protensity estimates appears not to be restricted to the block itself, but rather appears to pervade the entire communicative activity. The accuracy of such estimates appears to be related to the severity of the dysfluency.