At the start of the 1990’s, three synthetic materials were introduced : esters, ethers, and polyalphaolefins (PAO’s). Now heading toward the last half of this decade, a new generation of synthetics is gaining popularity-linear alpha olefins (LAO’s), internal or isomerized olefins (IO’s), and linear paraffins (LP’s). While similar, they also have differences, both as base fluids and as formulated drilling muds. These second-generation synthetic-based fluids (SBF’s) have benefits over their predecessors in that they have lower kinematic viscosity and are less expensive. As drilling fluids, these technical advantages give rise to a more flexible fluid to meet greater drilling demands for high-temperature-high-pressure (HTHP) applications, extended-reach-drilling projects, and deepwater drilling. As with the first-generation materials, environmental issues are the drivers for the development and use of these second-generation synthetics.