Abstract: Bogolubov's celebrated 1947 theory of Bose gases was invented to explain the superfluidity of liquid Helium. Only a few rigorous aspects of the theory have been validated rigorously. I will discuss cases of Bose gases in which Bogolubov's theory correctly predicts the ground state energy in certain asymptotic limits. In particular, I will discuss a recent proof of the famous Lee-Huang-Yang formula for the ground state energy of a dilute Bose gas. I will also briefly mention what may be derived from Bogolubov's method when applied to the charged Bose gas. This is joint work with E.H. Lieb.