Objective. To evaluate the quantitative measurement of diaphragmatic motion in healthy subjects and to investigate the effects of different variables such as body mass index and waist circumference on the diaphragmatic motion, Methods. The study included 164 healthy subjects. The subjects were grouped according to age, sex, body mass index, and waist circumference. Measurements of diaphragmatic motion were made by a 3.5-MHz sonographic unit in the M-mode of the system. The posterior diaphragm on both sides was identified, and measurements were per-formed during deep inspiration. Results. The mean diaphragmatic motion measurements +/- SD were 49.23 +/- 10.98 and 50.17 +/- 11.73 mm on right and left sides, respectively. Female subjects had statistically significantly (P < .05) decreased diaphragmatic motion (right, 46.93 +/- 10.37 mm; left, 47.57 +/- 10.36 mm) than male subjects. The mean diaphragmatic motion (right, 40.90 +/- 8.89 mm; left, 39.37 +/- 9.15 mm) was less in subjects who were underweight (P < .05) when compared with subjects who were of normal weight, overweight, and obese. Subjects who had a waist circumference of less than 70 cm showed a statistically significant decrease (P < .05) in diaphragmatic motion (right, 42.55 +/- 9.12 mm; left, 42.24 +/- 9.73 mm) when compared with subjects who had a waist circumference of 70 to 85, 85 to 100, and greater than 100 cm. Also, subjects younger than 30 years had statistically significantly (P < .05) decreased diaphragmatic motion (right, 44.57 +/- 10.57 mm; left, 44.44 +/- 11.37 mm). Conclusions. Sex, body mass index, waist circumference, and age may affect the diaphragmatic motion to some extent. Healthy persons of younger age with a smaller body mass index and waist circumference may show a decreased amount of diaphragmatic motion.