The technique of linear dichroism (LD) is a simple absorbance technique that uses two polarised light beams. Since only oriented molecules show different absorbances for different polarisations, LD detects only oriented molecules. In aqueous solutions, flow orientation is an attractive orientation methodology as it selects long molecules or molecular assemblies. LD thus is selective for molecules that are particularly challenging to study by more standard biophysical techniques. In this article, a brief review of the application of LD to DNA, DNA-drug systems, DNA-protein enzymatic complexes, fibrous proteins and membrane peptides and proteins is given.