Recent studies have underlined the impact of obesity on sperm parameters, but very few data are available on the effect of weight loss on male fertility. This article reports the case series of three male patients who underwent rapid and major weight loss following bariatric surgery and the consequences of this surgery on semen parameters and fertility. A severe worsening of semen parameters was observed during the months after bariatric surgery, including extreme oligoasthenoteratozoospermia, but azoospermia was not observed. This effect may hypothetically be the result of two opposite mechanisms: (i) the suppression of the deleterious effects of obesity; and (ii) the negative impact of both nutritional deficiencies and the release of toxic substances. Information about potential reproductive consequences of bariatric surgery should be given to patients and sperm cryopreservation before surgery proposed. However, for one case, the alterations of spermatogenesis were reversible 2 years after the surgical procedure. Finally, intracytoplasmic sperm injection with fresh spermatozoa after male bariatric surgery can be successful, as demonstrated here, where clinical pregnancies were obtained for two out of the three couples. (C) 2011, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.