An experimental study of primary breakup in the near-injector region of large-diameter (5.0 and 9.5 mm) liquid jets in still air is described. Holography was used to provide drop and liquid surface characteristics for initially nonturbulent liquids (water, n-heptane, and various glycerol mixtures) having various jet exit velocities. Drop sizes after primary breakup satisfied Simmons' universal root normal distribution and can be characterized solely by their Sauter mean diameter (SMD). The SMD increased with distance from the jet exit and then remained nearly constant within a fully developed primary breakup region. SMD measurements in the fully developed regime did not agree with existing expressions based on unstable surface wave growth. However, an expression based on stripping-type breakup due to boundary layer growth in the liquid along the windward side of surface waves yielded a reasonably good correlation of present SMD measurements. The nature of this primary breakup correlation implies that secondary breakup is a dominant feature of liquid-gas mixing layers.