The use of algorithms for calculation and analysis of RNA secondary structures has largely been limited to mainframe computers, mainly due to the 16-bit memory restrictions imposed by MS-DOS. The program presented here, RNAdraw, moves calculations to the 32-bit Microsoft Windows environments with an intuitive user interface with extensive viewing, editing and printing possibilities. The algorithms for secondary structure/basepair probability matrix/heat curve calculation have been ported directly from a 32-bit Unix environment. RNAdraw also offers novel features such as the options to edit energy parameters, extract structures of different probability levels, create de novo secondary structures interactively, and combine viewing of structures and basepair probabilities.