Sex-related differences affecting pharmacokinetic and pharmacodynamic processes result mostly from sex dimorphisms in body composition, and liver and kidney function, in addition to hormonal regulation of enzymes, transporters and drug receptors. Gender biases have long compromised the identification of these differences in clinical trials. They also modulate prescription patterns and therapeutic benefits. Men and women would benefit from different standard dosages of some anti-infectives, anticancer agents and other treatments requiring precise dosage adjustment. This would alleviate the well-documented excess of adverse reactions affecting women. However, the variability of pharmacological responses within each sex exceeds the average male-female difference, highlighting the importance of other criteria for therapeutic individualisation.