  We study the general dependence of mixing angles on heavy fermion masses when
mass hierarchies exist among the fermions. For two generations and small
Cabibbo angle, this angle is directly shown to scale like $\mu_1/m_s \pm
\mu_2/m_c$, where $|\mu_1| \ll m_s, |\mu_2| \ll m_c$ are independent mass
scales. For $n=3$ generations, we extend to the Yukawa matrices of $u$- and
$d$-type quarks the property that the $2\times 2$ upper-left sub-matrix of the
Cabibbo-Kobayashi-Maskawa matrix $K$ is a good approximation to the Cabibbo
matrix $C$. Then, without any additional Ansatz concerning the existence of
mass hierarchies or the smallness of the mixing angles, the moduli of its
entries $K_{13},K_{23},K_{31},K_{32}$ are shown to scale like
$[\beta_{13},\beta_{23},\beta_{31},\beta_{32}] \sqrt{{m_c}/{m_t}} \pm
[\delta_{13},\delta_{23},\delta_{31},\delta_{32}] \sqrt{{m_s}/{m_b}}$, where
the $\beta$'s and the $\delta$'s are coefficients smaller than 10. This method,
when used for two generations, gives a dependence on $m_s$ and $m_c$ ``weaker''
than the one obtained first, but which matches a well known behaviour for the
Cabibbo angle: $\theta_c \approx \sqrt{\epsilon_d (m_d/m_s)} -
\sqrt{\epsilon_u(m_u/m_c)}$, with $\epsilon_d,\epsilon_u \leq 1$. The
asymptotic behaviour in the case of three generations can also be strengthened
into a $1/m_{b,t}$ behaviour by incorporating our knowledge about the
hierarchies of quark masses and the smallness of the mixing angles.
