We report one-year's experience of home iv antibiotic treatment in 31 patients with cystic fibrosis chronically colonized with Pseudomonas aeruginosa. The patients were aged 4-67 years and had a mild to severe disease as indicated by a Shwachman score of 46-95 (mean 77). Ninety-two courses of iv antibiotic therapy were given (mean 3.0 per patient). The mean duration of the courses was 15.4 days. The entire antibiotic course, except for the first dose, was administered at home in 70% of the courses. Most patients (94%) were given a combined treatment of a beta-lactam and an aminoglycoside, administered by the patients themselves or their parents. One inserted venous cannula could be used for the whole treatment period in 30% of the courses. There were no complications. The clinical and bacteriological outcome was good to excellent in 89% of the courses, with temporary eradication or semi-quantitative decrease of Pseudomonas growth in sputum. Lung function (forced expiratory volume at 1 s) and blood gases improved significantly (p less than 0.001) and p less than 0.01, respectively). Most patients were able to attend work or school as usual, and 96% of the patients preferred this type of treatment to hospitalization. Apart from the psychosocial advantages, the economical savings were substantial. In comparison to traditional treatments in hospital (21 patients, 41 courses) home iv antibiotic treatment was safe and effective.