This study examined the effect of pre-slaughter handling (electrical, gas (CO(2)) or non-stunning) on lipid oxidation (as thiobarbituric acid reactive substances, TBARS; in the unit of mg malondialdehyde/kg(-1) of meat) of Spanish Manchega breed lamb meat, at 24h and at 7 days post-mortem. Lambs were slaughtered at two different weights (light (L), 25kg, vs. suckling (S), 12.8kg). In general gas-stunned lambs had lower lipid oxidation (P<0.001), and it was higher (P<0.001) in light lambs compared to suckling lambs. In both groups (S and L), malondialdehyde level increased with time (P<0.001), although this increase was lower (P<0.05) in gas-stunned suckling lambs. In addition, we evaluated the effect of stunning methods (TS: electrical vs. gas) and the weight (L vs. S) on lipid oxidation values in samples packed in different types of modified atmosphere (MA: A: 70%O(2)+30%CO(2); B: 69.3%N(2)+30%CO(2)+0.7%CO; C: 60%N(2)+40%CO(2)) at 7, 14 and 21 days post-packing. Values were higher in samples with MA-type A and lower in B and C types (P<0.05). A significant interaction (P<0.001) weight×TS was observed and the lowest rates of TBARS were found in the samples of light lambs stunned with gas and packed under anaerobic conditions (MA-B and C).