At global level, the microbiological quality of water is a matter of concern, since diarrhoea represents the second cause of mortality. In addition, nitrates represent a significant problem and their high concentration - above the accepted limits - in drinking water is frequently encountered in Romania. Water samples have been analyzed in accordance with the methodology recommended by The Public Health Institute Bucharest. 78.15% of the water samples evaluated during the interval 2004-2007 proved that they do not fit the quality norms. The frequency of the samples which do not meet the minimal requirements of the specific norms indicates an increasing tendency. The layered analysis of data has established ascending trajectories, inverse correlations and acceptable levels of association for both the out-of-norms microbiological samples and the physical-chemical.