Six papers on Human Machine Interfaces have been published from a new point of view. As one of the important technologies for developing optimal human machine interaction, communication between humans and machines has attracted much interest. In this special issue, the editor focuses on new methods for communicating mutual information on the characteristics of both human operators and machines, including computers and vehicles. In this communication, readers can operate machines easily and comfortably.

The first article, by Hiroshi Takahashi and Hirohiko Honda, studies the possibility of applying subliminal visual marks for informing drivers of hazardous factors without causing a nuisance in the driver-assistance systems.

The second paper, by Hiroshi Igarashi, proposes subliminal control parameter calibration in interactive human-machine operational environments. Subliminal calibration will enable users to master handling in a short time.

The third paper, by Hiroshi Takahashi and Hirohiko Honda, focuses on computer game operation as influenced by ultrasound exposure. The relationship between ultrasound signals and operator behavior is discussed.

The fourth paper, written by Hirohiko Honda and Kazuko Tobita, concerns the improvement of personal computer operation using auditory signals for visually handicapped persons, who can then identify operational processes through simple sounds.

The fifth contribution, by Hirohiko Honda, involves improving mouse operation with personal computers for those physically challenged who suffer progressive deterioration. The proposed system helps such users maintain quality of life because they are able to continue using a personal computer even as their state of mobility deteriorates.

The closing contribution, by Hiroshi Igarashi, Yoshinobu Adachi, and Kazunari Takahashi, deals with multiagent systems based on human social behavior. Adaptability and the total performance of the authorfs proposed technique are confirmed through a pursuit problem in a multiagent system.

We thank the referees for their reviews and the Fuji Technology Press Ltd. staff for its encouragement and advice.