A brief introduction to the subject regions, highlighting some key differences with respect to other known basins as well as the size of the prize, is followed by a focus on fluid properties' role in terms of field development and uncertainty reduction. The Tupi oil field, discovered in 2006 in the Santos basin 160 miles off the coast of Rio de Janeiro, and subsequent pre-salt discoveries transformed the nature and focus of Brazil's oil sector. These discoveries' impact on world oil markets could be significant. However, developing these resources will be challenging. Many technical hurdles must be overcome to access the oil, which occurs at great depths and high pressures below salt. Production from pilot projects is possible in the next several years, but large-scale development of the subsalt reserves probably will not occur until well into the decade.