Ruminant livestock systems emit CH4 and N2O to the atmosphere. Quantification of greenhouse gas (GHG) emissions in Spain is reported annually in the National Emission Inventory. The objective of this study was to update the annual CH4 and N2O emissions by dairy and beef cattle, and dairy ewes in the Basque Country of Northern Spain according to the recommendations of IPCC (2006) (Tier 2) using regional farm management data. A mathematical approach was used to assess uncertainties of estimated emission factors (EF). CH4 EF from enteric fermentation was 107kg CH4/hd/yr for dairy cattle with a milk yield of 7870kg milk/hd/yr. The corresponding values for beef cows and dairy ewes were 60 and 8.4kg CH4/hd/yr. Emission of CH4 from enteric fermentation accounted for 87% of total CH4 emissions in ruminant production, with dairy and beef cattle the main contributors. The regional contribution of beef cattle to enteric CH4 emissions has become important recently as many farmers have changed from dairy to beef cattle production. CH4 EF (Tier 2) from manure management was 33.2, 2.0 and 0.3kg CH4/hd/yr for dairy cattle, beef cattle and dairy ewes. From 2005, many small dairy cow farms (