Stair design and environmental conditions may play a role in slip accidents on stairs in the workplace, but little is known about the slip resistance requirements on stairs compared to level walking. Older adults have an increased risk of falling compared to younger adults and may be at greater risk during stair negotiation. The purpose of this study was to determine whether the ground reaction force profiles and peak required coefficient of friction (RCOF) differed between young and elderly women or between stair ascent, stair descent and overground walking. While there was a trend towards less risky stair descent behaviour in the older women in terms of their peak RCOF values during stair descent, the increased vertical loading rate in the older women may imply reduced dynamic balance control. The largest mean RCOF peaks occurred during stair ascent in both young and older women, but there were several overground walking trials in both groups and a few stair descent trials of the young women, which resulted in RCOF peaks greater than 0.5. These results should be considered when choosing stair surface materials, particularly in occupational and outdoor settings where the tread surfaces may become wet or contaminated.