Activity of group-transported horses was evaluated during onboard rest stops to determine if horses derive meaningful rest. A single-deck semi-trailer separated into three compartments was used for all shipments. In Experiment One, twelve video cameras were used to record behavior of horses during five, 16 to 20 h shipments, with a high (397.44kg/m2), medium (348.48 kg/m2) and low (220.91 kg/m2) density group in each shipment. One-hour rest stops occurred after 8 h of transport and prior to unloading, during which two groups were provided water. Movement of each horse visible on video was quantified by counting the number of times the head crossed the vertical and/or horizontal axes of the body at the withers. Mean number of movements per 5-min interval in each group (n=13) was used to compare effects of density, access to water, and order of stops. The high and low-density watered groups had increased activity during the first 10 min of both rest stops potentially due to maneuvering for access to water. The medium-density watered groups had increased activity during the first 10 min of only the second rest stop. Activity slightly increased in the medium and low-density groups after 55 min possibly indicating adequate rest, but a similar increase did not occur in highdensity groups. In Experiment Two, two shipments, lasting 23 h and 24 h respectively, consisted of three groups of horses loaded at high density (397.32 kg/m2). Ninety-minute rest stops occurred after every 6 h of transport and prior to unloading for a total of three rest stops. Percentage of visible horses "active" was averaged across each 5-min interval of the stop. Activity was highly variable within and between shipments. Activity was high at the beginning of stops one and three of Shipment One. A similar but less dramatic settling occurred at the start of all three rest stops in Shipment Two. Twenty three of thirty-four noted increases in alertness were due to aggression or noises outside the trailer. In both experiments horses remained active during all stops indicating fatigue had not become a major factor in these studies.