Little is known about male reproductive strategies in aquatically mating pinnipeds. To study the mating patterns of harbour seals, Phoca vitulina, VHF telemetry was used to relate the distribution and behaviour of adult males to the distribution of females during the summer pupping and mating season. Prior to July males occupied large and variable ranges. At the beginning of July, males decreased their mean range size, but continued to spend much of their time in the water where they made characteristic short dives. Acoustic recordings in the presence of several radiotagged males suggested that these short dives were associated with underwater vocal displays. Throughout July, males varied in the geographical areas which they used to perform these displays. Some individuals were found in the water around haul-out sites; others were located on foraging grounds, up to 50 km from pupping sites, and some were consistently located displaying on transit routes between these two areas. This study supports previous suggestions that vocalizations and diving displays may be associated with male mating behaviour, but suggests that males may display over a much wider geographical area than was previously recognized. This system of dispersed but small display territories is suggestive of lekking. However, further research on the distribution of the clumping of displaying males is required to confirm this.