This book reports the Proceedings of the NATO Advanced Research Workshop on "An gular Momentum Evolution of Young Stars" held from 17 to 21 September 1990 at Noto, Italy. The workshop had its immediate origin in a discussion about the availability of stel lar rotation data, that took place in 1987 at Viana do Castelo Portugal during the NATO meeting, Formation and Evolution of Low Mass Stars. We recognized that nearly 20 years had passed since the last meeting on stellar rotation and that significant progress in the observation of rotation rates in low mass stars had been made. During the last 20 years, new efficient instrumentation (CCD and photon counting de tectors and echelle spectrographs) and new analysis techniques (profile Fourier analysis) have allowed us to measure rotational velocities as low as 1-2 km/s and to reach low mass stars in young clusters. Even with these advances, rotational velocities of low mass stars would have remained challenging to determine if all single, low mass stars later than GO had rotational velocities of order or less than 10 km/sec. Evidence that this is not always the case was first provided by the photometric variability data obtained by van Leeuwen and Alphenaar for K dwarfs in the Pleiades and more recently by the vsini measurements of low mass stars in several young clusters."

I. Initial Angular Momentum Distribution.- Angular Momentum Effects in Star Formation.- Evolutionary Properties of Intermediate-Mass Protostar.- Small-Scale Structure and Angular Momentum Transfer in Protostellar Environments.- Ekman Pumping in a Rotating Protostar.- Rotation in Pre-Main Sequence Stars; Properties and Evolution.- Disks Associated with Intermediate Mass Stars.- Differential Rotation of Fully Convective Pre-Main Sequence Stars.- The X-ray Emission from PMS Stars in Taurus-Auriga, and the Relationship with Other Diagnostics of Activity.- Multifrequency Monitoring of RU Lupi; Observational Results and a Model.- Polarimetry and CCD Imaging of Herbig Ae/Be Stars and Star Forming Regions.- II: Angular Momentum Evolution.- Rotational Velocities of Low Mass Stars in Young Clusters.- Rotation of Young Stars in the Orion Nebula Region.- Rotational Velocities of Stars in Open Clusters; the Time-Dependence Revisited.- Main Sequence Angular Momentum Loss in Low-Mass Stars.- The Angular Momentum Evolution of Young and Old Binary Components.- Ages of Spotted Late-Type Stars.- Rotation of Evolved Stars.- Rotational Discontinuity of Evolved Stars; What Interpretation?.- III: Consequence of Rotation.- Magnetic Activity and Rotation.- Lithium, Rotation and Age.- Rotation, Chromospheric Activity, and Lithium Abundances in G and K Dwarfs of the Pleiades.- Lithium Abundance and Rotation in Southern Chromospherically Active Stars.- Lithium Depletion Induced by Rotation in Young Stars.- Rotational Mixing and Lithium in Young Stars.- IV: Internal Rotation and Models.- Internal Solar Rotation.- Stellar Activity Belts as Potential Indicators of Internal Rotation and Angular Momentum Distribution.- Dynamics of Spot Groups and Rotation of the External Convective Layers in the Sun and Magnetically Active Stars.- Theory of Magnetic Braking of Late-Type Stars.- Pre-Main Sequence and Main Sequence Rotational Evolution; Constraints on Models Derived from Observations.- Evolutionary Models of Rotating Stars.- The Internal Rotation of the Sun; Implications on the History of its Angular Momentum.- Angular Momentum Transport, Rotational Instabilities, Magnetic Fields and Mixing.- The Spin-Down of Main Sequence Stars Based on Observed Magnetic Field Strength.- Session V: Observational Perspectives.- Observational Perspectives.- PRISMA: a Space Facility for Studying Rotation and Activity.- The Spectrum-UV Project.- Summary of the Workshop.- Panel Discussion: Initial Angular Momentum.- Panel Discussion: Dynamos and Internal Rotation.- Author Index.- Object Index.