Atomistic Monte Carlo simulations of polymethylene fluids in various e
nvironments have been of great importance for improving our understand
ing of the molecular arrangements and-conformations in systems of chai
n molecules. This paper describes models, calculations and principal r
esults of a number of simulations performed in the last two decades fo
r liquid alkanes in bulk and in the proximity of solid surfaces, and f
or systems of long chain amphiphilic molecules in monolayers, double l
ayers, micelles and droplets.