Mitochondrial replacement techniques (MRTs) usually aim to prevent the genetic transmission of maternally inherited mitochondrial diseases. Until now, only the UK and Australia have implemented specific legal regulations of MRTs. In both countries, clinical trials on these techniques are only permissible for cases with a high risk of severe mitochondrial disease in the offspring. However, these techniques can also be applied to treat infertility, especially for older women with impaired oocyte quality. In some countries without legal regulation of these techniques, (...) MRTs are already offered for this purpose. Yet, this application of MRTs has received insufficient attention in the bioethical literature so far.In this paper, I examine whether there are ethical reasons to prohibit trials on MRTs in the context of infertility when they are permitted for preventing mitochondrial disease. Allowing MRTs in one context but not the other might be justified either because their application in the context of mitochondrial disease (1) is supported by a more convincing evidence base, (2) has a higher potential benefit or (3) has a lower risk. I compare both applications of MRTs with respect to these three factors. I conclude that there is no convincing reason to prohibit clinical trials on MRTs for infertility when they are permitted in the context of mitochondrial disease. (shrink)