  Let $A_n$ denote the height of cyclotomic polynomial $\Phi_n$, where $n$ is a
product of $k$ distinct odd primes. We prove that $A_n \le
\epsilon_k\phi(n)^{k^{-1}2^{k-1}-1}$ with $-\log\epsilon_k\sim c2^k$, $c>0$.
The same statement is true for the height $C_n$ of the inverse cyclotomic
polynomial $\Psi_n$.
  Additionally, we improve on a bound of Kaplan for the maximal height of
divisors of $x^n-1$, denoted by $B_n$. We show that $B_n<\eta_k
n^{(3^k-1)/(2k)-1}$, with $-\log \eta_k \sim c3^k$ and the same $c$.
