The Mitogen Activated Protein Kinases (MAPKs) are stimulated by various types of stress. Repeated exposure to psychological stress leads to increased levels of phosphorylated p38 MAPKs, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) levels in the brain. However, effects of psychological stress have not been extensively studied in peripheral tissue, particularly skeletal muscle. Restraint stress has been shown to increase p44/p42 ERK in the rat heart and 1 day of hindlimb suspension has been shown to activate p38 MAPK in rat soleus muscle. Therefore, the purpose of this study was to determine levels and phosphorylation status of various MAPKs in gastrocnemius muscle after chronic psychological stress. Adult male Wistar rats were used. Animals in the Immobilisation stress group (I; n = 10) were subjected to immobilisation for 2 hours/day for 28 days. For these 2 hours the animals were placed in small cages preventing movement. Animals in the Control (C) group were not immobilized (n = 10). After 28 days of stress (or control), 24 hours after the last exposure to immobilisation, animals were decapitated, blood was collected and gastrocnemius muscle was removed. Levels of total and phosphorylated p38, ERK 44, ERK 42 and JNK were measured by western blot analysis, and corticosterone levels by radioimmunoassay (RIA). ANOVA was performed and specific differences were identified using Bonferroni correction. Statistical significance was accepted at P<0.05; data are presented as mean ± SD. Chronic stress significantly increased basal serum corticosterone (I: 81 ± 11 vs C: 22 ± 7 ng/ml, p < 0.001) demonstrating the stress response. There were significantly increased levels of phosphorylated p38 MAPK (I: 137.5 ± 8.67 vs C: 70.93 ± 7.44; p < 0.001) and phosphorylated 44kD ERK (I: 118.70 ± 5.11 vs C: 72.61 ± 9.23 p 0.05). The results demonstrate that upregulation of p38 MAPK and ERK 44 may play a role in the response to chronic psychological stress in skeletal muscle of rats.