Most characteristics of language use are continually changing as time goes by. Studies describing linguistic change have so far largely ignored the area of speech planning processes and their observable consequences in spontaneous speech. In the present paper, disfluency phenomena were analyzed in two corpora recorded half a century apart. Present-day speakers' spontaneous speech is significantly more interspersed with disfluency phenomena (a total of 1754 occurrences in our data) than that recorded fifty years ago (568). Statistical analyses have revealed that hesitations, repetitions and error-type phenomena occur significantly more frequently with present-day speakers. In the earlier speakers' speech planning processes, the operation of lexical processes ran into more difficulty, whereas present-day speakers had more problems with finding the appropriate grammatical and phonological structure as well as with the monitoring of their transformations of thought into linguistic material. Underlying the differences observed in the occurrence of the various disfluency phenomena, an increasing amount of information that speakers now have to handle and their altered communicative needs can also be detected.