Though rapid changes are likely to occur, until recently most Mediterranean countries had neither water reuse regulations nor guidelines. Countries where reuse is developing within an organized institutional setting have elaborated and implemented their own regulations or guidelines. Some countries (France, Tunisia) and regions (Andalusia and Balearic Islands in Spain and Sicily in Italy) have adopted a set of water quality criteria based on the WHO guidelines, while other countries (Cyprus, Italy, Israel) elaborated regulations or guidelines close to the more conservative California's Water Recycling Criteria. Though the need for sharing common regulations or, at least, a common rationale for developing water reuse standards on both sides of the Mediterranean has been acknowledged, this objective does not appear reachable in a near future. Among the factors that might be evoked to explain the dramatic discrepancies in the Mediterranean criteria, the lack of a clear rationale supported by scientifically established data as a solid basis for setting up water reuse guidelines has a major importance. A deterministic approach, such as the one adopted in the draft of Australian National Guidelines for Water Recycling may, despite several drawbacks and uncertainties, pave the way to reach a regional consensus.