We have characterized the telomeres of four species within the genus Saccharomyces, S. castellii, S. dairensis, S. exiguus and S. kluyveri. S. exiguus contains the same type of telomeric repeats as S. cerevisiae and they show the same kind of irregularity. S. kluyveri contains a 26 bp telomeric repeat with a 15/16 match to the C. glabrata repeat. In analogy with the long Candida repeats, these repeats are all completely identical. S. castellii and S. dairensis were found to share the same 8 bp telomeric sequence, TCTGGGTG which is identical to half the 16 bp C. glabrata repeat, and furthermore highly resembles the S. cerevisiae sequence. 76% and 64% of the respective S. castellii and S. dairensis repeats are identical basic 8 bp repeats. The majority of variant repeats present in S. castellii are composed of the basic repeat followed by a varying number of extra TG dinucleotides, which closely resembles the irregularity found in S. cerevisiae. Although the same type of variant repeats are also present in S. dairensis, the majority here constitutes a 6 bp repeat lacking the TG dinucleotide, which has not been detected in S. castellii. The S. castellii results suggest that the variants may be produced during synthesis of telomeric DNA by slippage of the telomerase template. In contrary, if telomerase is responsible for the production of the S. dairensis variants, it would supposedly be caused by a premature termination of the synthesis.