In a previous study with erythromycin lactobionate it was shown that a 12-hour intravenous infusion of 2 g produced peak plasma erythromycin concentrations well above the required levels to inhibit the growth of all standard erythromycin-sensitive pathogens (including Haemophilus influenzae). Unfortunately two subjects vomited after receiving 2 litres of normal saline (in which the erythromycin lactobionate was infused). For this reason it was decided to administer half the previous dose of erythromycin lactobionate in 500 ml of 0.9N saline over 1 hour. The present study shows that the latter dose regime produces therapeutic plasma erythromycin base concentrations in the plasma in all subjects, five of whom also participated in the previous study. The infusions were well tolerated in every participant. More rapid administration enabled the baseline pharmacokinetics of this parenteral erythromycin salt to be established by two different computer programmes in healthy volunteers. It is hoped that the data outlined in this paper will prove a useful baseline for future studies with erythromycin lactobionate in healthy volunteers and patients with severe infections who receive this antibiotic.