Broad band time domain spectroscopy (TDS) methods for the measurement of dielectric relaxation phenomena are described, and applied to aqueous systems in the time range approximately 10–10 to 10–4 s. Relaxation measurements on aqueous solutions of amino acids, peptides, proteins, and small carbohydrates and on frozen aqueous systems (ice and ice-clathrates) are reported. It is shown how the measurements can be performed rigorously using a Fourier transformation procedure, but how in certain cases a simple time domain analysis can lead to results of acceptable accuracy. The value of these multiple reflection approaches in relation to existing TDS methods, and their potential application to dielectric studies in more highly conducting media, are discussed.