The aim of the present study was to determine the effects of a 4-week exercise training intervention on blood glucose, insulin sensitivity, BMI (body mass index) and cardiorespiratory fitness in patients with Type 2 diabetes, and to identify and establish criteria for patients who are more likely to improve their blood glucose from short-term exercise training. A randomized, controlled trial of exercise training, comprising two supervised and one non-supervised sessions of individualized cardiorespiratory and resistance exercise per week, was performed in 132 healthy patients with Type 2 diabetes (exercise training group, n = 68), with the aim of accumulating a minimum of 150 min of moderate-intensity exercise for 4 weeks. BMI, waist circumference, blood pressure, blood lipid profile, blood glucose, insulin, insulin sensitivity [calculated by HOMA(IR) (homoeostasis model assessment of insulin resistance) and QUICKI (quantitative insulin check index)], beta-cell function (calculated by HOMA(beta-Cell)), HbA(Ic) (glycated haemoglobin) and (V)over dotO(2max) (maximal oxygen consumption) were measured at baseline and at 4 weeks. The exercise training group had significant improvements in (V)over dotO(2max) BMI and triacylglycerols (triglycerides). There were no significant changes in blood glucose, HOMA(IR), QUICKI or HOMA(beta-Cell). Decreases in blood glucose were significantly predicted by baseline blood glucose and HbA(Ic), with these variables accounting for 15.9% of the change in blood glucose (P <0.001). ROC (receiver operator characteristic) curve analysis revealed that patients with a blood glucose > 8.85 mmol/l (sensitivity = 73%, specificity = 78%) and HbA(Ic) > 7.15% (sensitivity = 79%, specificity = 60%) were more likely to achieve a clinically significant decrease in blood glucose. In conclusion, in apparently healthy patients with Type 2 diabetes, a 4-week exercise intervention improved cardiorespiratory fitness, BMI and triacylglycerols. Elevated blood glucose and HbA(Ic) predicted improvements in blood glucose.