Water is one of the most important substances in the nature that finds wide field of application in the pharmaceutical industry. Water being located in the nature has not always an acceptable purity grade for manufacturing of the final pharmaceutical products. The water quality for pharmaceutical usage because of its assignment is laid down by the National Quality Standards (pharmacopeia), which minimally should be harmonized with recommendations of the World Health Organization. The most common water form that finds use in the pharmaceutical industry is the water for injection (WFI). The work presents process of preparing WFI in one Croatian pharmaceuticals plant. For the purpose of quality monitoring of the WFI produced by the distillation process, appropriate quality of potable water, softened water, purified water and WFI during production process and using is confirmed. The quality of the WFI is monitored through samples that have been analyzed in the internal laboratory and by continuous monitoring of process parameters on the water control system that blocks the use of the WFI of inadequate quality.