This study was designed, to analyze the incidence of SARA in the course of a long term feeding trial in a dairy herd in early lactation. A trial was performed to investigate the effects of feeding barley treated chemically to reduce rumen degradability of its starch. As ruminal pH values were the same between the feeding groups, the data were used to analyze the continuously measured ruminal pH values of these 30 fresh lactating cows. The pH-measurements were performed using a real-time wireless measurement system with an indwelling pH sensor. The aim of the study was to investigate the ruminal pH-development and its individual and diurnal changes. A few criteria were used for the interpretation of the pH-data, i.e. the mean ruminal pH as well as the time/day of the ruminal pH being below certain values. These criteria enabled the identification of cows suffering from SARA (subacute rumen acidosis). Although the cows were fed intensively, the prevalence of SARA observed in this study was far below reported values from literature. Different results were found, depending on the threshold level used to define SARA and depending on the use of mean pH or the time below pH 5,8 or pH 6,0. The age of the cows as well as their dry matter intake and the time since the last meal were found to have an influence on the ruminal pH. These results underline the importance of a valid method for the pH-measurement in terms to identify animals at risk of developing SARA. In practice, prevention plays the major role in controlling SARA on a herd level, being even more important due to the limited possibilities of measuring ruminal pH in individuals.