Two major long-term complications of Diabetes mellitus (DM) are neuropathy and skeletal atrophy which decrease the quality of life for the diabetic patients. This study investigated the effect of streptozotocin (STZ)-induced DM on EDL and soleus skeletal muscle contraction and on sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), zinc (Zn²⁺), iron (Fe²⁺) and copper (Cu²⁺) levels in the two muscle types of male Wistar rats compared to age-matched controls. DM was induced by a single (i.p.) injection of STZ (60 mg kg^-1). Control rats received an equivalent volume of citrate buffer. DM was confirmed 4-5 days after STZ injection and 6-8 weeks later using a glucose meter. Contraction was measured using an isometric transducer and the muscles were stimulated electrically (EFS) at an amplitude of 50 V, 1 ms pulse duration and at 1-100 Hz. At the end of the experiment, each muscle was blotted, weighed and dissolved in concentrated nitric acid. Cation contents in the muscles were measured using an atomic absorbance spectrophotometer. Data are presented as mean ± SEM, n= 8-10 rats for each parameter. Prior to STZ injection, the rats weighed 161.13±1.41 g, (n=22). Diabetic rats gained significantly (p<0.05) less body weight (222.19±10.51 g) and muscle weights (EDL; 0.17±0.02 g; soleus 0.17±0.02 g) compared to age-matched control body (501.83±25.91 g) and EDL (0.21±0.05 g) and soleus (0.23±0.02 g) weights. Diabetic rats also have significantly (P<0.05) elevated blood glucose (29.65±0.33 mM) and significantly (p<0.05) reduced plasma insulin level (4.81±1.28 mg dl^-1) compared to control (glucose, 6.06±0.21 mM; insulin, 20.63±7.52 mg dl^-1). EFS evoked frequency-dependent (10-100 Hz) contraction in both soleus and EDL muscles of healthy control and diabetic rats with a maximum response at 40-50 Hz. Higher frequencies caused a small reduction in contraction. The force of contraction was significantly (P<0.05) elevated in EDL muscle (4.39+0.36 N cm^-2, n=8) compared to soleus muscles (1.53±0.26 N cm^-2, n=8) at 50 Hz. In both diabetic EDL (1.19±0.05 N cm^-2, n=8) and soleus muscles (0.31±0.01 N cm^-2, n=8), the force of contraction was significantly (P<0.05) reduced compared to the respective control at 50 Hz. The levels of total Na⁺, K⁺, Ca²⁺, Mg²⁺, Zn²⁺, Cu²⁺, and Fe²⁺ in both muscles were significantly (P<0.05) reduced in diabetic rats compared to control animals. Typically, the levels of Na⁺, K⁺, Mg²⁺ and Ca²⁺ in control EDL muscle were 0.432±0.014, 0.121±0.004, 0.037±0.002 and 0.025±0.0007 mM (100 mg tissue)^-1 compared to 0.210±0.004, 0.071±0.001, 0.022±0.0004, 0.005±0.0008 mM (100 mg of tissue)^-1 in diabetic EDL muscle, n=8-10. Similarly, levels of Na⁺, K⁺, Mg²⁺ and Ca²⁺ in control soleus muscle were 0.351±0.023, 0.131±0.008, 0.029±0.002 and 0.023±0.0005 mM (100 mg tissue)^-1 compared to 0.100±0.001, 0.03±0.001, 0.004±0.0007, 0.003±0.0004) mM (100 mg of tissue)^-1 in diabetic soleus, n=8-10. The results indicate that diabetes is associated with significant reductions in the force of contraction and cation contents in EDL and soleus muscles. The reduced cation contents in turn may be responsible for the development of muscle atrophy and reduced force of contraction since they are associated with electrical activities and cell signalling processes in skeletal muscles.