OBJECTIVES: Studies about the efficiency of pre-hospital antibiotic treatment of meningococcal disease are conflicting. We examined the case fatality rate in patients with meningococcal disease treated with pre-hospital antibiotics. METHODS: A cohort study of 534 patients hospitalized with meningococcal disease from two Danish counties. Clinical data were obtained from referral letters from general practitioners and hospital records. Complete follow-up for all patient until death or discharge. RESULTS: Seventy-seven patients (16% of the patients seen by a general practitioner) received parenteral antibiotics before hospital admission; 9 (12%) of them died. Of 402 patients who did not receive pre-hospital parenteral antibiotics, 26 (7%) died. The overall risk of case fatality among antibiotic-treated patients was increased with adjusted odds ratio (OR) = 2.4 (95% CI, 1.0-5.6). Meningococcus serogroup B was associated with increased case fatality in patients who received pre-hospital parenteral antibiotics (OR = 2.6; 95% CI, 0.8-8.3) in contrast to other serogroups. In Aarhus County there were no deaths in patients who received pre-hospital parenteral antibiotics, but in North Jutland County the case fatality was high (OR = 2.9; 95% CI, 1.2-6.8). CONCLUSIONS: The efficiency of pre-hospital parenteral antibiotic treatment seems to be dependent on hospital care and may vary with the serogroup.