Felton, C. A., Colazo, M. G., Bench, C. J. and Ambrose, D. J. 2013. Large variations exist in prepartum activity among dairy cows continuously housed in a tie-stall barn. Can. J. Anim. Sci. 93: 435-444. Electronic activity monitoring might assist with the early detection of calving; however, little work has been done to determine if dairy cows housed in tie-stalls changed their activity as calving approached. The objectives were to describe retrospectively, prepartum activity changes in cows housed in tie-stalls using AfiMilk pedometers, and determine if restless activity preceding parturition differed between primiparous and multiparous cows. Twelve primiparous and 12 multiparous Holstein cows housed in tie-stalls were monitored daily by pedometers for 9 d immediately preceding their calving date. Fifteen consecutive hours (1700 to 0800) of activity was recorded during each 24-h period, when cows remained continuously in their stalls, until day -1 (calving = day 0). Activity data from days -9 to -3 were available from all 24 cows, and up to day -1 from 16 cows; based on these data, there was an overall average increase in stepping activity of 34% (range, 32% decrease to 119% increase) from day -2 to day -1. However, only 56% of cows exhibited a 10% or more increase in stepping activity. Primiparous cows tended to have increased stepping activity (1366 ± 116 vs. 1039 ± 116 steps; P = 0.06) and decreased lying bouts frequency (7.5 ± 0.6 vs. 8.1 ± 0.6; P = 0.07) than multiparous cows. They also had significantly shorter lying durations (376 ± 23 vs. 473 ± 23 min; P < 0.01) than multiparous cows. Holstein cows housed continuously in tie-stalls manifested large variations in prepartum activity. Primiparous cows had significantly shorter lying durations than multiparous cows, and tended to have higher mean stepping activity. Further characterization of prepartum activity in dairy cows housed in tie-stalls and the use of steps-to-lying ratio could be valuable to detect imminent parturition, particularly in primiparous cows.