On this thesis, author have tried to determine effective specific gravity (ρ) of developed silver grains dispersed in developed emulsion layer. The relationship between the mass of developed silver per unit area (M), the number of developed silver grains per unit area ( N ), the developed grain volume (υ), and the effective specific gravity of developed silver grain (ρ) are indicated theoretically by next equation. M = N ·υ·ρ The mass of developed silver were determined by potentiometric titration. The number of developed silver grain per unit area, the developed grains size frequency distribution and the average grain diameter were calcurated by the newly developed counting method based on the electronmicroscopical observation of developed layer cross-section. The volume of developed grain were calcurated from the above mentioned grain size frequency distribution histogram by approximating grain shape as sphere. Hence we can calcurate the effective specific gravity by substitute these three values (M, N, and υ) in above equation. On this experiment, we have used Neopan-F 120 film as experimental material and fixed developing conditions as follows, D -76; 20°C; 14 min., and D -72 (1: 2); 20°C; 5 min. Determined each average effective specific gravity ρ _{D -76} and ρ _{D -72} were 1.539 and 1.10, respectively, and in the case of solution physical development concerning with ordinary chemical development just as D -76, the values of ρ are generally higher than D -72 (1: 2) and gradually decrease with increasing D, on the contrary in the case of mainly chemical development is occuring as D -72, the values of ρ are almost constant and does not change with D . Interrelations between D, N, M, d and ρ of a bove mentioned experimental conditions are showed and discussed, too.