The effect of machine milking on udder health has been recognized for the past 100 years and many studies have been conducted in order to show the detrimental effects of conventional clusters since these systems result in permanent deformation of udders and scarred teat canals. Due to these unwanted effects of conventional systems (CON), a new quarter-individual milking system called the Multilactor (R) (MULTI) (Siliconform GmbH, Turkheim, Germany) has been developed in the last five years. The objective of this study was to determine the effects of milk flow on average liner vacuum during the b- and d-phase of pulsation in both systems by using the milking-time test defined by International Dairy Federation (IDF, 1999). Measurements were conducted in two different milking parlours where a conventional milking system (CON) and MULTI were installed separately. The vacuum data during milking were examined and the milk flow curve was recorded using a LactoCorder (R) (WMB, Balgach, Switzerland). It was found out that, at an average flow rate of approximately 5.0 I/udder/min, the average vacuum in the liner during the b- phase was 30.2 kPa in CON and 27.7 kPa in MULTI system which was not significantly different. In contrast the average liner vacuum during the d-phase was significantly different between the systems. It was 28.5 kPa for CON and 16.3 kPa for MULTI. This big difference is caused by the Multilactor (R) using the BioMilker (R) system (Siliconform GmbH, Turkheim, Germany) that allows periodic air ingress to the pulsation chamber.