Middle Sister is in the Three Sisters Wilderness of Central Oregon and is a committed alpine climb - it cannot be considered a hike as there is not a 'trail' to the top. It's about 14 miles round trip, 4800 feet net gain and took us over 13 hours.
It's recommended you prepare carefully, reading guidebooks and climbing websites, and making sure you have the necessary skills, experience and equipment and team. You will need to be able to handle wilderness route finding, high angle snow ascent and descent, rock climbing, and challenging terrain. Adequate physical conditioning is critical to ensure success and safety. Each of your party members needs to prepare in kind.
From the junction of Highway 20 and 242 in Sisters, Road 15 (Pole Creek Road) is 1.5 miles. Take this west about 10.5 miles to the trailhead. From here, the Pole Creek Trail heads south through a burn. You'll be turning off this trail to head towards Middle Sister. See detailed guidebooks.
We camped overnight at the Pole Creek Trailhead (44.187445° -121.700258°) and started in the dark. This made for a very long day. Some folks camp after turning off the Pole Creek Trail towards the Hayden Glacier - that might make for a more pleasant experience.
We roped up for some snow travel experience on the snowfield that parallels the Hayden Glacier - although we could see crevasses we weren't too concerned about them on this part of the mountain.
From the saddle above the glacier the final pitches get pretty serious with slopes up to perhaps 45 or 50 degrees. Upon arriving at the summit, the clouds closed in and we elected to make the summit stay very short at less than five minutes. I was able to work just two stations on 2m FM in that time, and although I heard other folks, they weren't hearing me and it was time to turn the radio off and focus on a safe descent.
More information on the Pole Creek Trailhead can be found here: http://www.fs.usda.gov/recarea/deschutes/recarea/?recid=71839 and here: http://www.summitpost.org/north-ridge-via-hayden-glacier/155622. Trail conditions: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5299503.pdf
