Participatory Fisheries Stock Assessment (ParFish) Software is a PC-based software package that uses Bayesian Statistics and Decision Theory to assess the state of a fishery stock and estimate limit and target control levels. The software supports the overall approach which is described in the accompanying ParFish Guidelines. The guidelines provide an overview of all six steps in the approach including: i) understanding the context; ii) engaging stakeholders; iii) undertaking the stock assessment; iv) interpreting the results and giving feedback; v) initiating management planning and vi) evaluating the process. The ParFish software is currently based on the logistical biomass growth model and requires information on four parameters: Current Biomass, Unexploited Biomass, Catchabilty and Growth rate. Interview data from fishers are used to construct 'priors' for the model parameters which can be combined with other available information to provide best estimates. This information is then used, together with preference data from fishermen, to calculate the current stock level and the control levels that will provide the most preferred catch rates for fishers. The programme takes explicit account of uncertainty in the data, presenting results as probability density functions (with accompanying mean, median, mode and confidence intervals). The Software is accompanied by a manual which gives step-by-step guidance on inputting data and running the analysis. There area also additional reference sheets which assist with the interviews and other data collection methods.