Abstract: Rumex obtusifolius and Rumex crispus are problematic grassland weedy species, particularly under conditions of organic farming. They are avoided by cattle and horses, but they can be grazed by goats. The aim of this study was to investigate the effectiveness of continuous goat grazing of moderate intensity on R. obtusifolius and R. crispus control. In 2008, 40 seedlings of each species were transplanted into pasture that was grazed by goats (crossbreed Czech white × Czech brown) on the target sward height of 7–10 cm. The number of leaves, proportion of grazed leaves and mortality of plants were monitored over the following 4 years. The number of leaves per plant was higher for R. obtusifolius than for R. crispus. The maximal number of leaves per plant of R. obtusifolius and R. crispus was 10 and 5, respectively. The proportion of grazed leaves was generally higher for R. obtusifolius than for R. crispus and ranged from 10% to 80%. No fertile plant was recorded during the experiment, as goat grazing totally prevented the flowering of both species. The level of mortality of the plants at the start of the fourth grazing season was 70% and 87% for R. obtusifolius and R. crispus, respectively, and no plant survived the fourth grazing season. It was concluded that continuous goat grazing of a moderate intensity that is carried out over 4 years seems to be an effective method for the non-chemical control of R. obtusifolius and R. crispus in grassland. [Michal Hejcman, Lukáš Strnad, Pavla Hejcmanová & Vilém Pavlů (2014). Biological control of Rumex obtusifolius and Rumex crispus by goat grazing. Weed Biology and Management, online 9 April 2014.