Serum neutrophil chemotactic activity (NCA) was measured in patients with acute severe asthma (status asthmaticus) and compared with that in control subjects (mild asthma, stable chronic irreversible air-flow obstruction, allergic rhinitis, noninfective lung conditions, or asymptomatic). There were 9 subjects in each group. Statistically significant elevations (p less than 0.002) in NCA were detected in acute severe asthma when compared with each control group. Serial measurements of NCA were subsequently undertaken in 12 patients with acute asthma, at the time of admission to hospital, after 3 days of treatment, and on discharge after approximately 7 days. A highly significant (p less than 0.001) reduction in serum NCA activity on Day 7 compared with that on Day 0 was observed, and this correlated inversely with the improvement in lung function (PEFR). Gel filtration by fast protein liquid chromatography (FPLC) using Superose 6 prep grade (6PG) indicated that NCA in acute severe asthma was heterogeneous and consisted of at least 4 peaks of activity associated with proteins with molecular weights of approximately 800, 600, 150, and less than 20 kD. The 800- and 150-kD peaks were also observed in control subjects, but to a lesser degree. The 600- and less than 20-kD activities were virtually confined to the patients with acute severe asthma. FPLC chromatofocusing of the 600-MW peak from the acute asthmatics, using a Mono-P column and a pH gradient from 8.3 to 5.0, revealed considerable activity in fractions eluting between pH 6.0 and 7.0, which was not observed in the normal control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)