Proceedings of IAU Symposium No. 68 held in Buenos Aires, Argentina, 11-14 June 1974, organized by the IAU in co-operation with COSPAR1: General Solar Activity, Coronal Holes and Bright Points.- EUV Observations of the Active Sun from the Harvard Experiment on ATM.- Holes in the Solar Corona.- Time Variations of Solar X-ray Bright Points.- Solar Activity Observed in X-Rays and the EUV from OSO 7.- 2: Active Regions.- X-Ray Spectra of Solar Active Regions.- X-Ray Spectroscopy of Solar Active Regions During the Third Skylab Mission.- Spatially Resolved X-Ray Spectra of Coronal Active Regions.- Classification of New Spectral Lines of Fe XVII Observed in Solar Active Regions.- Statistical Methods in the Identification and Prediction of the Solar X-Ray Spectral Lines.- Interpretation of the X-Ray Spectra of Solar Active Regions.- Soft X-Radiation from Single Active Regions.- Time Variations in Coronal Active Regions.- Flare-Like Ultraviolet Spectra of Active Regions.- The Structure of Solar Active Regions from EUV and Soft X-Ray Observations.- 3: Solar Flares.- Ultraviolet Emission Line Profiles of Flares and Active Regions.- Fe XXIV Emission in Solar Flares Observed with the NRL/ATM XUV Slitless Spectrograph.- X-Ray and EUV Spectra of Solar Flares and Laboratory Plasmas.- Association of X-Ray Flares with Solar Coronal Active Regions.- Studies of the Dynamic Structure and Spectra of Solar X-Ray Flares.- On the Thermal Structure of the Flare-Produced Plasma.- The Relationship between Hard and Soft X-Ray Bursts Observed by OSO 7.- Relationship between Hard and Soft Solar X-Ray Sources Observed by OSO 7.- Thermal and Nonthermal Interpretations of Flare X-Ray Bursts.- High Time Resolution Analysis of Solar Flares Observed on the ESRO TD-1A Satellite.- Rise Time of Hard X-Ray Bursts.- Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons.- Inference of the Hard X-Ray Source Dimensions in the 1972, August 7, Wl3Å