The purpose of this study was to examine the validity of the Smarthealth watch (Salutron, Inc., Fremont, California, USA), a heart rate monitor that includes a wristwatch without an accompanying chest strap. Twenty-five individuals participated in 3-min periods of standing, 2.0 mph walking, 3.5 mph walking, 4.5 mph jogging, and 6.0 mph running. Heart rate was simultaneously measured and recorded at 60-sec intervals using three methods: the Smarthealth wristwatch, the Polar Vantage XL monitor with an accompanying chest strap (Kempele, Finland), and an electrocardiograph, which served as the criterion method. The heart rates obtained from the Smarthealth watch were highly correlated with those from the electrocardiograph (r greater than or equal to 0.95) and the standard error of estimate was below 5 bpm for all measurements. Additionally, correlation coefficients and standard errors of estimate between the Smarthealth watch and Polar heart rate monitor were greater than or equal to 0.97 and less than 3.7 bpm, respectively. However, the Smarthealth watch exhibited a reduced ability to detect a heart rate during the 4.5 and 6.0 mph conditions compared to the Polar heart rate monitor (6% and 13.9% reduced ability, respectively). The Smarthealth watch appears to be a valid device for monitoring heart rate while standing and during treadmill exercise involving walking and jogging in a healthy young adult sample, although it may not be able to consistently detect a heart rate when body motion is excessive. (Contains 2 figures and 2 tables.)