Structured Systems Analysis and Design Methodology (SSADM) is a systems approach to the analysis and design of information systems. SSADM was produced for the CCTA, a UK government office concerned with the use of technology in government, from 1980 onwards.

System design methods are a discipline within the software development industry which seek to provide a framework for activity and the capture, storage, transformation and dissemination of information so as to enable the economic development of computer systems that are fit for purpose.

SSADM is a waterfall method by which an IS design can be arrived at; SSADM can be thought to represent a pinnacle of the rigorous document-led approach to system design, and contrasts with more contemporary Rapid Application Development methods such as DSDM.

SSADM is one particular implementation and builds on the work of different schools of development methods, some of the key members of which included:

• Peter Checkland, developer of the Soft Systems Methodology , an instance of Systems thinking
• Chris Gane & Trish Sarson, authors of Structured Systems Analysis: Tools and Techniques
• Ed Yourdon, developer of the Yourdon method in Structured programming
• Michael A. Jackson, developer of Jackson Structured Programming

The SSADM method involves the application of a sequence of analysis, documentation and design tasks concerned with:

• Analysis of the current system
• Outline business specification
• Detailed business specification
• Logical data Design
• Logical process design
• Physical design

The design of SSADM has changed a number of times since its first release, informed by user experience and by other and newer methodologies. In particular SSADM has developed to apprehend a greater need for iteration, even to the point of the use of the methodology within or as an adjunct to RAD projects. Despite the changes, SSADM in particular, and the waterfall approach in general is criticised for adding to the time and cost of software projects without improving the outcome or output of the projects.

SSADM was for a number of years a recommended practice in the development of UK government information systems, along with the PRINCE method. More recently the Unified Modeling Language approach has been recommended by CCTA's successor, the Office of Government Commerce.