We report an unusual case of juvenile ischaemic stroke syndrome associated with the A8344G mutation in tRNA(Lys) gene of mitochondrial DNA. The clinical phenotype of patient was typical for MELAS (mitochondrial ecephalomyapathy with lactate acidosis and stroke like episodes). The MELAS has been related to mutation A3243G in most cases, but some other mitochondrial DNA mutations were described in the background of this syndrome as well. A 22-years-old man and his family were investigated. Throughout clinical investigation as well as Doppler sonography, neuroradiological, and immunserological examinations were performed. Molecular studies included the analysis of the Leiden, prothrombin G20210A and the most common mitochondrial DNA mutations. The DNA analysis of the proband revealed a heteroplasmic A8344G substitution in the T-loop of the tRNALYS gene. The mutation could not been detected in her mother blood. We can conclude that A8344G mutation of the mitochondrial DNA resulted in juvenile ischemic stroke, which is associated only rarely to this genetic alteration. In young age onset of a stroke-like episode with undetermined etiology the mtDNA alterations always have to be excluded.