Experimental measurements were made, in a specially designed wind tunnel, of the impaction efficiency on cylinders, spheres, ribbons and discs of uniform-droplet aerosols. Droplets from 20–40 μ dia. were used in wind speeds of 2–6 m/sec impacting on objects measuring 0·1–2·9 cm wide. Impaction efficiencies on cylinders and spheres were generally similar to the limited experimental data already available and were slightly below the theoretical values. Ribbons and discs were substantially less efficient collectors than indicated by accepted theory. Comparison of smoke flow in a wind channel with theoretical curves showed deviations consistent with the observed impaction differences.