The most obvious method of interaction is direct communication between two or a few colleagues; 31% of the survey respondents stated that they communicate daily or several times per week with other astronomy librarians, 40% a few times per month, 23% a few times per year, 6% never. In addition, astronomy librarians are also in contact with non-astronomy librarians: 33.5% contact them daily or several times per week, 26% a few times per month, 33.5% a few times per year, 7% never.
Electronic mail has brought upon us a communication revolution, and it has quickly grown to become the most frequent method of communication. The ease and speed of writing email messages points towards even increased use in future. Never before was it so convenient to contact colleagues instantly, allowing them to reply whenever they find the time and opportunity to do so. Even though the internet ``netiquette'' defines guidelines for email, everybody is rather free to compose messages according to personal preferences in language, grammar, style, and content. This seems to be an irresistible advantage of electronic communication as opposed to letters on paper, telephone conversations and even personal contacts. A clear majority of 62.5% of the survey respondents listed email as their most frequent method of corresponding with colleagues. The second most common method, namely meeting face to face in their libraries (including other staff in their own library), falls far below that at 19.5%. But email as the first choice of communicating with colleagues varies, quite predictably, between developed and developing countries: while 63% of the respondents from the former group noted email as the most frequently used medium, only 53% of the respondents from the latter group did so.