  In this paper we shall deal with periodic groups, in which each element has a
prime power order. A group $G$ will be called a $BCP$-group if each element of
$G$ has a prime power order and for each $p\in \pi(G)$ there exists a positive
integer $u_p$ such that each $p$-element of $G$ is of order $p^i\leq p^{u_p}$.
A group $G$ will be called a $BSP$-group if each element of $G$ has a prime
power order and for each $p\in \pi(G)$ there exists a positive integer $v_p$
such that each finite $p$-subgroup of $G$ is of order $p^j\leq p^{v_p}$. Here
$\pi(G)$ denotes the set of all primes dividing the order of some element of
$G$. Our main results are the following four theorems. Theorem 1: Let $G$ be a
finitely generated $BCP$-group. Then $G$ has only a finite number of normal
subgroups of finite index. Theorem 4: Let $G$ be a locally graded $BCP$-group.
Then $G$ is a locally finite group. Theorem 7: Let $G$ be a locally graded
$BSP$-group. Then $G$ is a finite group. Theorem 9: Let $G$ be a $BSP$-group
satisfying $2\in \pi(G)$. Then $G$ is a locally finite group.
