Despite the growing quantity of literature exploring the effect of caffeine on muscular strength, there is a dearth of data that directly explores differences in erogenicity between upper and lower body musculature and the dose response effect. The present study sought to investigate the effects of low and moderate dose caffeine on the maximal voluntary strength of the elbow flexors and knee extensors. Ten non-specifically strength trained, recreationally active participants (21 ± 0.3 yrs) completed the study. Using a randomised, counterbalanced and double blind approach, isokinetic concentric and eccentric strength was measured at 60 and 180 deg/s following administration of a placebo, 3 mg・kg-1 body mass caffeine and 6 mg・kg-1 body mass caffeine. There was no effect of caffeine on the maximal voluntary concentric and eccentric strength of the elbow flexors, or the eccentric strength of the knee extensors. Both 3 and 6 mg・kg-1 body mass caffeine caused a significant increase in peak concentric force of the knee extensors at 180 deg/s. No difference was apparent between the two concentrations. Only 6 mg・kg-1 body mass caused an increase in peak concentric force during repeated contractions. The results infer that the effective caffeine concentration to evoke improved muscle performance may be related to muscle mass and contraction type. The present work indicates that relatively low dose caffeine treatment may be effective for improving lower body muscular strength, but may have little benefit for the strength of major muscular groups of the upper body.