Abstract-We investigate the computation of Csiszár's bounds for the joint source-channel coding (JSCC) error exponent of a communication system consisting of a discrete memoryless source and a discrete memoryless channel. We provide equivalent expressions for these bounds and derive explicit formulas for the rates where the bounds are attained. These equivalent representations can be readily computed for arbitrary source-channel pairs via Arimoto's algorithm. When the channel's distribution satisfies a symmetry property, the bounds admit closed-form parametric expressions. We then use our results to provide a systematic comparison between the JSCC error exponent and the tandem coding error exponent , which applies if the source and channel are separately coded. It is shown that Index Terms-Discrete memoryless sources and channels, error exponent, Fenchel's duality, Hamming distortion measure, joint source-channel coding, random-coding exponent, reliability function, sphere-packing exponent, symmetric channels, tandem source and channel coding.