In a General Hospital in San Sebastian, 96 cases of Neisseria meningitidis infections were detected in a two years period. By the use of the disk diffusion method, we found that all causative meningococcal strains but 4 were resistant to sulfonamide (with a 300 microgram sulfadiazine disk, all isolates with a zone diameter of less than 20 mm were considered to be resistant of sulfadiazine, whereas those with zone diameters of greater than 30 mm were considered susceptible). No rifampin nor minocycline-resistant meningococci were isolated. All strains had a disk zone diameter (30 micrograms rifampin and 30 micrograms tetracycline) of greater than 20 mm. The serogroups of meningococcal strains were as follows: group A, 1; group B, 67; group C, 5 and 23 were no typed. Children less than four years of age were most frequently attacked (67,7%). The attack rate was only slightly higher in males than in females (52 and 44).