The reaction-diffusion equation u(t) = DELTAu(m) + f(u), with f(u) a p
olynomial or exponential function of u, is considered. Upper and lower
bounds, numerical routines and similarity solutions are all used to d
iscuss the phenomena of finite-time blow-up. In particular, the simila
rity solution for f(u) = u(m) provides evidence that the set of blow-u
p points does not necessarily have zero measure. Critical conditions f
or varying m are found numerically.