Seminal fructose, sperm count, and sperm motility were measured in 340 men attending an infertility clinic. Seminal fructose correlates negatively with sperm count but not with sperm motility. The best correlation between sperm count and seminal fructose was obtained using the logarithm (log) of sperm count. When seminal fructose was multiplied by the log of sperm count obtaining a value named "corrected fructose," the correlation with sperm count disappeared, and there was positive correlation between corrected seminal fructose and sperm motility. Therefore, corrected seminal fructose level was significantly lower in asthenospermic than in normomotile subjects, irrespective of the sperm count. Corrected seminal fructose, but not seminal fructose levels, was lowered in subjects with either low levels of serum testosterone (< 3 ng/ml) or evidence of an obstructive process in the reproductive tract. In both situations sperm motility was also reduced. The corrected fructose level was not affected by the presence of varicocele, hyperprolactinemia, or hyperserotoninemia. Measurement of corrected seminal fructose rather than seminal fructose may be a useful marker of the secretory activity of the seminal vesicles. © 1988 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.