This half marathon is to raise funds for malaria protection and control.
The seventh Race against Malaria is organised by Zara Charity, the Rift Valley Athletics Club and sponsored by the Ngorongoro Conservation Area Authority and telecommunications company, Tigo.
The run goes from the Ngorongoro crater to Karatu, about 80 kms west of Arusha, between Lake Manyara and the Ngoronogoro Conservation Area. There is also a 2.5 km fun-run.
Last year just over 500 runners participated, compared with about 150 the year before. This year the organisers are encouraging corporate teams to enter the race.
The marathon is designed to mark World Malaria Day on 25 April. This year the theme of the day, which was first instituted in 2007, is Invest in the Future. Defeat Malaria to highlight the continued need for investment and political commitment to eradicate the disease.