Abstract: A system (10) particularly suited for employment for purposes of effectuating the monitoring, diagnosing and controlling of the chemistry of the water and steam in a steam generator steam cycle (46). The subject system (10) is operative to monitor water and steam quality at a number of critical locations (70,72,74,76) in the steam generator steam cycle (46). Based on the information gathered through such monitoring of water and steam quality, the subject system (10) is designed to be operative to provide diagnoses of potential causes of upsets in the steam generator steam cycle chemistry and to suggest corrective actions as appropriate. Furthermore, historical data is also readily available from the subject system (10) which can be utilized for identifying trends and for assessing the operational chemistry of the steam generator steam cycle (46) both on a short-term basis and on a long-term basis.