Representative isolates of nonmucoid Pseudomonas aeruginosa were studied to investigate the hypothesis that mucinophilic and chemotactic properties in this species act as potential factors in the initial stages of pulmonary colonization in patients with cystic fibrosis (CF). Transmission electron microscopy with a surfactant monolayer technique was used in a novel manner to demonstrate the adhesion of all 10 P. aeruginosa strains examined to porcine gastric mucin and tracheobronchial mucin from a patient with CF. Control experiments showed that Escherichia coli K-12 and single representatives of Proteus mirabilis and Klebsiella aerogenes did not bind to these mucins. The Adler capillary technique, used to measure bacterial chemotactic response, showed that purified CF mucin acted as a chemoattractant for most P. aeruginosa strains, with the exception of the nonmotile mutant M2Fla- and the nonchemotactic mutant WR-5. The ability of the major sugar and amino acid components of mucin to act as chemoattractants was investigated. The degree of chemotaxis was strain specific; optimum chemotaxis was observed toward serine, alanine, glycine, proline, and threonine. No strain showed chemotaxis to N-acetylneuraminic acid, but all strains showed a strain-dependent chemotactic response to the sugars L-fucose, D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine. These results provide new information on the mucinophilic and chemotactic properties of nonmucoid P. aeruginosa and support the hypothesis that these properties could play a role in the initial stages of pulmonary colonization in patients with CF.