A frequently asked question shortly after an earthquake occurs is "What is the probability of that earthquake being a foreshock of a stronger one?". The answer lies in the past seismicity of the area of interest, so it is necessary to analyze the earthquake catalogue. This in particular is the topic of this thesis. After the earthquakes are determined to be foreshocks, mainshocks or aftershocks, the aftershocks are disregarded in future analysis. Then, the percentage of foreshocks among earthquakes of magnitude M is calculated. This percentage represents the probability we are trying to determine for the earthquake of interest. This thesis also studies the impact of the choice of parameters which define foreshocks and aftershocks on the probability for different magnitudes, and calculates weighted probabilities to get the most relevant results. In addition to the one for the whole of Croatia and nearby areas, a separate analysis was performed for the wider area of Pannonian Croatia and the Dinarides. Calculations show that, in general, for the whole area and for all the magnitudes, the probability is 10.5%. Earthquakes of magnitudes from 3.4 to 4.0 have the largest probability - approximately 12% - of being foreshocks. Results for the Dinarides are similar with probabilities that are around 0.5% larger, while they are somewhat lower when it comes to Pannonian Croatia - for all the magnitudes, the probabilities are around 8%, while the maximum probability of 12% occurs for the magnitudes from 4.5 to 5.0.