Annapurna is the 10th highest mountain in the world and was the first 8000m peak to be climbed. It was first summited in 1950 by Maurice Herzog and Louis Lachenal. It was not until 1970 that Annapurna was summited again. In the autumn of 1999 there were 120 expedition to Annapurna. 106 climbers reached the summit. 54 climbers never came back.
However, I am assuming you are more interested in trekking the Annapurna region , so most of this information will pertain to trekkers considering this trip.

When To Climb:
The usual trekking season in Nepal is from October to May. The rest of the year is the monson season and is not desirable for either trekking or expeditions. Besides the cold and rain, leeches are a problem during the monsoons. If you are going to be trekking to Annapurna, October and November are the best months.

Mountain Conditions:
Trekking possibilities are quite varied, but most will start at Pokhara. The circuit trek to the Annapurna Sanctuary will take at least 10 days, but allow 14 to have time to enjoy it and to allow for unforseen events. The route up the narrow Modi Khola river valley is quite wet and slippery and quite steep in a few places. It can be a bit dangerous. The trail up to the Annapurna basecamp is a more serious undertaking

ITINERARY:

Day 1: Arrive in Kathmandu, Transfer to Hotel
Day 02-03: Prepared Expedition & Briefing in Ministry of Tourism
Day 04: Drive Besi Sahar
Day 05: Besisahar- Nagdi
Day 06: Nagdi -Jagat
Day 07: Jagat -Tal
Day 08: Tal -Chame
Day 09: Chame - Pisang
Day 10: Pisang -Sabji Khola
Day 11: Sabji Khola - Annapurna 4th Base camp
Day 12- 28: Climbing Period Annapurna 4th Expedition
Day 29: Base Camp - Mananag
Day 30: Manang - Thorong Phedi
Day 31: Phedi - Thorong La pass - Muktinath
Day 32: Muktinath - Jomsom
Day 33: Jomsom - Kalopani
Day 34: Kalopani - Tatopani
Day 35: Tatopani - Beni
Day 36: Beni - Drive to Pokhara
Day 37: Drive to Kathmandu
Day 38-39: Kathmandu
Day 40: Final Departure

Cost: Ask for Quotation.

Nepal Expedition Programs:
Amadablam/ Pumori Expedition Annapurna Expedition Annapurna South Expedition Boruntse Expedition Dhaulagiri Expedition Everest Expedition	Everest North Expedition Lhotse Expedition Makalu Expedition Manaslu Expedition Pumori Expedition Shishapangma Expedition