Eight different mastitis remedies were administered intracisternally on a rotational basis to the 48 quarters of 12 mastitis negative cows. The resulting intramammary reactions were monitored by determining the Somatic Cell Count (SCC) and Bovine Serum Albumin (BSA) levels in milk. The reactions observed indicate that the intramammary cellular reactions frequently elicited by the local treatments in the treated and sometimes even in the untreated quarters of the treated udders are not necessarily inflammatory in nature. Evaluation of the intramammary tissue compatibility of a mastitis remedy mainly in terms of SCC values therefore seems unreliable. Moreover, it may do injustice to a product unless the SCC values are augmented by BSA or other determinations providing a more accurate indication of truly mastitic reactions. The investigation also implies that the patterns of cellular reactions related to individual mastitis remedies require further elucidation before they can be used as indications of an advantageous or disadvantageous intramammary tissue compatibility of a product. Intramammary tissue compatibility, as such, of mastitis remedies and comparable agents requires definition. It seems more expedient, however, that such a definition and the necessary standardization of mastitis remedies in terms of their intramammary tissue compatibility be attempted by the International Dairy Federation (IDF).