Efficacy and Safety of 24 Weeks of Oral Treatment With BIIL 284 BS in Adult and Pediatric Patients

INCLUSION CRITERIA: * Male or female patients \>= 6 years pediatric 6-17 years inclusive; adult \>= 18 years) * Body weight \>= 20 kg (determined at Visit 1) * Confirmed diagnosis of CF * Able to perform acceptable spirometric maneuvers, according to American Thoracic Society standards . * FEV1 25-85% predicted * Clinically stable * The patient or the patient's legally acceptable representative must be able to give informed consent. * The patient must be able to swallow the BIIL 284 BS tablets whole. * Patients taking a chronic medication must be willing to continue this therapy for the entire duration of the study. EXCLUSION CRITERIA: * Patients with a significant history of allergy/hypersensitivity (including medication allergy) which is deemed relevant to the trial as judged by the Investigator. "Relevance" in this context refers to any increased risk of hypersensitivity reaction to trial medication; there are no specific issues of concern currently identified with respect to use of BIIL 284 BS in allergic patients per se. * Patients who have participated in another study with an Investigational drug within one month or 6 half-lives (whichever is greater) preceding the screening visit. * Patients with known relevant substance abuse, including alcohol or drug abuse. * Female patients who are pregnant or lactating, including females who have a positive serum pregnancy test at screening (pregnancy tests will be performed for all females of child bearing potential). * Female patients of child bearing potential who are not using a medically approved form of contraception. * Patients who are unable to comply with food requirements prior to dosing. * Patients with documented persistent colonization with Burkholderia cepacia. * Patients chronically using oral corticosteroids or high-dose ibuprofen. * Patients with hemoglobin \< 9.0 g/dL; platelets \< 100x10 to the 9th power/L; SGOT (ALT) or SGPT (AST) \> 2.5 times the upper limit of normal; creatinine \> 1.5 times upper limit normal. * Clinically significant disease or medical condition other than Cystic Fibrosis or Cystic Fibrosis-related conditions that, in the opinion of the Investigator, would compromise the safety of the patient or the quality of the data.