[en] On the basis of the levels of many physical properties, such as density and elastic modulus, beryllium metal is well suited for use in the construction of high precision inertial navigation instruments, such as gyroscopes. However, a prime requirement of the materials used in these instruments, is that they are dimensionally stable. Consequently an investigation has been made of the dimensional stability of beryllium which has been investigated as a function of its chemistry, heat treatment and fabrication history. Only the inherent dimensional stability has been investigated, that is, the stability of the material when not subjected to any external stress. Studies of this stability were made at both normal ambient temperatures and at 343 K the equilibrium operating temperature of gyroscopes. A comparator type of experimental method was used which was capable of resolving length changes of the order of one microstrain. Gross instability was observed only in the case of heavily machined beryllium and even then was of a short term nature and was attributed to the time dependent relief of machining induced internal stresses. (author)