Vortex ring formation was motivated by a laboratory experiment of Didden which appears in Van Dyke's "An Album of Fluid Motion" (p. 43). At time t=0, a piston begins pushing fluid through the open end of a circular tube. The boundary layer separates and rolls up to form a vortex ring which propagates downstream. The piston stops moving at t=1.6 and thereafter a counter-rotating ring forms at the tube opening. In the simulation results shown below, the shear layer is represented by a free vortex sheet and the circular tube by a bound vortex sheet. Axisymmetric is imposed. Prandtl's slip-flow model is applied to simulate separation at the edge of the tube. High spatial resolution PIV measurements using film recording have yielded detailed instantaneous 2-D velocity fields of the formation of orifice generated vortex rings. The resultant high spatial resolution vorticity distributions enable the location and magnitude of regions of both primary and secondary vorticity to be determined. The experimental measurements demonstrate how secondary vorticity produced at the piston hastens the transition to turbulence. Vortex rings are usually formed by a brief discharge of fluid from an orifice. In previous investigations, the geometry of the vortex generator has varied greatly from one experiment to another, with important consequences for the ensuing flow. The present work categorizes the generating conditions for vortex rings and classifies the conditions under which a given vortex generator produces either an initially laminar ring, which may or may not undergo instability and transition to turbulence, or an initially turbulent ring. A particularly simple vortex generator was devised and measurements were carried out to provide systematic data over a range of the important dimensionless parameters. The results of this survey are used to construct a transition map that reveals a reasonably well defined boundary separating vortex rings that are turbulent upon formation from those that are not. Highâ€speed cinephotography of the formation and evolution of turbulent vortex rings suggests a possible connection between the generating conditions and the transition to turbulence.