The study of resistance patterns of strains of bacteria to antibiotics in different regions of a country and, if possible, comparing them at international level appears to be a useful exercise. The patterns of resistance during 1968-71 revealed an increasing resistance for most antibiotics with an unexpected increase for chloramphenicol. Notable is a decreasing resistance, not only of coagulase-positive strains of Staphylococcus aureus but also of other micro-organisms towards doxycycline. For practical purposes there was no difference between the sensitivy of the isolates from hospitalized patients and from out-patients, though less pronounced in the latter. The incidence of resistance among strains isolated from the paediatric ward was low. Comparatively small changes in molecular structure may result in relatively large differences in the sensitivity pattern; for example, between tetracycline and doxycycline (Vibramycin, Pfizer), the greatest activity is seen with doxycycline.