Seismic Toolkit is a tool for processing and displaying seismic signal data in a graphical interface. It reads seismic signals in SAC format, and provides a variety of signal processing, such as filtering, spectral analysis, polarisation analysis, time-frequency representation, Hilbert transform, and singular value decomposition. Some utilities are included for useful seismological applications, like computation of Seismic Moment Mo, Mantle magnitude Mm and Moment magnitude Mw, MTPA spectral analysis, plotting focal mechanisms, computation (and plotting) of instrumental response from poles and zeros, and some usefull GMT (Generic Mapping Tool) scripts for plotting signals, responses, and time-frequency in Postscript files for high quality prints. Changes: Compilation problems due to deprecated functions were solved with less restrictive pre-processor directves. A new utility program, Cairo_SAC, was added for plotting (in PDF, PS, or PNG) a large number of SAC files using Cairo functions.