We performed a longitudinal analysis of the effects of repeat botulinum toxin (BTX) injections in 42 patients with blepharospasm (BL) and 115 patients with cervical dystonia (CD) who received BTX injections between 1984 and 1992 in at least five separate treatment sessions. Although the BL patients were significantly older (59.8 years) than the CD patients (50.6 years; p < 0.001), there were no other demographic differences between the two groups. While the total dose per treatment session and the peak effect rating remained the same, the duration of benefit increased and the number of complications decreased during the course of treatment. We conclude that chronic treatment with BTX in patients with BL and CD is not associated with any decline in benefit, and that efficacy may improve slightly with repeat treatments.