1. Manuscripts can be submitted in Spanish, English, German and French. Under certain circumstances papers may also be published in other European Community languages. All papers will include an abstract and keywords in English and Spanish. 

2. Manuscripts should usually not exceed 20 A4 printed pages (29.5 x 21 cm), including figures and tables. For longer manuscripts, contact the editor. Manuscripts should be submitted on diskette on Word 6.0 or 7.0 (for PC). Three paper copies of the manuscripts (for editorial use and review) should be submitted as well. The paper copies should be double-spaced throughout, including tables, figure texts and references. 

3. Figures and tables must be of high quality and should be submitted on separate sheets of paper with the number of the figure or table indicated lightly in pencil at the bottom of the page. Figure legends should be numbered with arabic numerals and given on a separate sheet of paper. Figure and table legends should be concise and informative. 

4. Papers should be organized as follows: Title, name and mailing address(es) of author(s), Abstract, Keywords, Introduction, Materials and Methods, Results, Discussion, Conclusions, Acknowledgements, References. Results and Discussion may be treated together if this is appropiate. Non-experimental works can be organized in the way which the author(s) think(s) is the most appropiate one. 

5. Citations in the text should be with author and date of publication, e.g., (Smith, 1992) or (Smith & Jones, 1992) with comma between author and date; for two-author papers, cite both authors; for papers by three or more authors, use Martín et al., 1993. For two or more papers with the same author(s) and date, use, a, b, c, etc., after the date. 

6. References: only papers cited in the text should be included; they should be arranged as follows: 

PÉREZ, C.; RODRÍGUEZ, P. & DÍAZ, J. (1960): Ecological factors and family size. Journal of Bioethics, 21: 13-24. 

RUÍZ, L. (1980): The Ecology of Infectious Diseases. Siglo XXI, Madrid.