Fructose is secreted from the seminal vesicles and the accessory sex glands. It is the major carbohydrate source in seminal plasma and essential for normal sperm motility. The objective of this prospective descriptive study was to measure fructose concentrations in seminal plasma from men with obstructive and non-obstructive azoospermia, as determined by serum FSH, and to compare these with fructose concentrations in seminal plasma from men with normal semen parameters. A higher median fructose concentration was observed in seminal plasma from men with azoospermia and a raised serum FSH (3.22 mg/ml) compared to that from men with azoospermia and normal serum FSH (2.30 mg/ml) (p < 0.0001) and to that from normal controls (2.50 mg/ml) (p < 0.0002). This is the first report of increased seminal plasma concentrations of fructose in samples from men with non-obstructive azoospermia. This is either due to a decreased fructose metabolism associated with the azoospermia or, more likely, an increased fructose production from the seminal vesicles.