The paper discusses the latest developments in the ATSAS program package (version 2.4) for processing and analyzing isotropic small-angle X-ray and neutron scattering (SAXS and SANS) data. Key improvements include: 1. **Multiplatform Data Manipulation and Display**: The ATSAS 2.4 release includes cross-platform versions of data analysis tools like PRIMUS and SASPLLOT, supporting Windows, Linux, and Mac OSX. 2. **Automated Data Processing**: New programs such as AUTOMERGE for automated merging and extrapolation of multiple data sets, and AUTOPOROD for automated determination of particle volume and molecular mass. 3. **Enhanced Structural Model Integration**: Improved algorithms for using high- and low-resolution models from complementary methods like X-ray crystallography, NMR, and electron microscopy. 4. **Three-Dimensional Model Building**: New algorithms for building models from weakly interacting oligomeric systems and complexes, including GASBORMX and SASREFMX for flexible systems. 5. **Analysis of Mixtures and Flexible Systems**: Enhanced tools for analyzing mixtures with known scattering profiles and flexible systems, including RANLOGS for generating random loops and CORAL for modeling complexes with missing fragments. 6. **Online Services and Documentation**: The release includes web-based interfaces for major ATSAS programs, an online forum for user support, and an improved user documentation system. These developments aim to enhance the functionality, performance, and usability of the ATSAS package, making it more accessible and powerful for researchers in physics, materials science, and biology.The paper discusses the latest developments in the ATSAS program package (version 2.4) for processing and analyzing isotropic small-angle X-ray and neutron scattering (SAXS and SANS) data. Key improvements include: 1. **Multiplatform Data Manipulation and Display**: The ATSAS 2.4 release includes cross-platform versions of data analysis tools like PRIMUS and SASPLLOT, supporting Windows, Linux, and Mac OSX. 2. **Automated Data Processing**: New programs such as AUTOMERGE for automated merging and extrapolation of multiple data sets, and AUTOPOROD for automated determination of particle volume and molecular mass. 3. **Enhanced Structural Model Integration**: Improved algorithms for using high- and low-resolution models from complementary methods like X-ray crystallography, NMR, and electron microscopy. 4. **Three-Dimensional Model Building**: New algorithms for building models from weakly interacting oligomeric systems and complexes, including GASBORMX and SASREFMX for flexible systems. 5. **Analysis of Mixtures and Flexible Systems**: Enhanced tools for analyzing mixtures with known scattering profiles and flexible systems, including RANLOGS for generating random loops and CORAL for modeling complexes with missing fragments. 6. **Online Services and Documentation**: The release includes web-based interfaces for major ATSAS programs, an online forum for user support, and an improved user documentation system. These developments aim to enhance the functionality, performance, and usability of the ATSAS package, making it more accessible and powerful for researchers in physics, materials science, and biology.