Registration is now open for the annual Mercer Island Rotary Run Half Marathon, to benefit colon cancer research and early detection.

The races include a half-marathon run/walk (13.1 miles), a 10k run (6.2 miles), a 5k run/walk (3.1 miles), and the Kid’s Dash of (½ mile). Online registration at mercerislandhalf.com has begun and continues through March 20. Entry forms are also available Club Emerald on Mercer Island.