First break picking is a pattern recognition problem in the area of seismic signal processing, a problem difficult to automate and that requires a lot of human effort to be solved. The objective of this project was to develop an algorithm, based on Fuzzy Inference Systems, using fuzzy rules of the form If ‐ Then to perform automatically first break picking in VSP data. The results indicate that by the implementation of this algorithm the maximum error obtained is of 2ms compared to first breaks calculated manually. However, when the signal to noise ratio (S/N) is low, the algorithm's accuracy decreases.