A method of isolation has. been developed to purify mast cells from human lung tissue. The purification steps are: (1) dispersion of human lung tissue in single‐cell suspensions by enzymatic digestion, (2) partial purification by counterflow centrifugal elutriation, (3) Percoll gradient centrifugation, and (4) enrichment of the mast cells by affinity chromatography using anti‐human IgE‐Sepharose. Enzymatic dispersion yielded 0.6±0.2×106mast cells per gram wet tissue with purities of 3.3±1.0% (mean ±SIMn=3). Elutriation and gradient centrifugation yielded 0.36±0.05×10% mast cells per gram lung tissue in fractions with purities of 30.8±10.7%. Enriched mast cell Fractions were combined, and disposed of contaminating cells by affinity chromatography, thereby yielding 0.25±0.03×106mast cells per gram lung tissue, and improving the purity to 75.3±8.3%. The purified mast cells were intact and vitality exceeded this way from 1 g wet lung tissue 0.25±0.03×106mast cells may be isolated with a mean recovery of 41.7±2.4% and a mean p