Penicillin resistant and multiresistant pneumococci have become common all over the world. Pneumococci resistant to cefotaxime and ceftriaxone have only become established in the USA, Spain and South Africa, although recently such strains have been described in the UK. Resistance to cefotaxime and ceftriaxone may spread faster than penicillin resistance. With B-lactam resistant and multiresistant pneumococci, the choice of antimicrobials is reduced to a single class of antimicrobials, the glycopeptides. Penicillin resistant pneumococci were introduced in Iceland in 1988, and had gained 20% incidence in pneumococcal infections in 1993. This rapid spread was associated with serogroups 6, 19 and 23, of which serotype 6B (multiresistant) was by far the most prevalent. During this period the incidence of penicillin resistant pneumococci remained low in the other Nordic countries. Since the practice of medicine is very similar in these countries, it was important to search for epidemiological clues that would explain the difference. The following risk factors have been shown to be important in epidemiological studies conducted in Iceland: most Icelandic children attend day-care centres, where they have numerous contacts with children with respiratory tract infections during the long winter months. Antimicrobial usage was high in children attending day care centres. The popularity of the sulpha-trimethoprim combination in Iceland may also be important, as it was shown to be an independent risk factor. Total use of antimicrobial agents declined in Iceland in the years 1991-1993 following a propaganda campaign against misuse and legislative changes that increased the cost of the antimicrobials for patients. The antimicrobial use in day-care centres was significantly reduced from 1992 to 1995. In 1994 the incidence of penicillin resistant pneumococci decreased to 17% (from 20% in 1993). Hopefully reduction in antimicrobial use will continue and contribute to further lowering of resistance levels.