Objective: To examine the frequency distribution of co-existing conditions for deaths where the underlying cause was infectious and parasitic diseases.Materials and methods: Besides the underlying cause of death, the distributions of co-existing conditions for deaths from infectious and parasitic diseases were examined in total and by various age and sex groups, at individual and chapter levels, using 1998 Australian mortality data.Results: In addition to the underlying cause of death, the average number of reported co-existing conditions for a single infectious and parasitic death was 1.62. The most common co-existing conditions were respiratory failure, acute renal failure ' non-specific causes, ischaemic heart disease, pneumonia and diabetes. When studying the distribution of co-existing conditions at the ICD-9 chapter level, it was found that the circulatory system diseases were the most important. There was an increasing trend in the number of reported co-existing conditions from 60 years of age upwards. Gender differences existed in the frequency of some reported co-existing conditions. The most common organism types of co-existing conditions were other bacterial infection and other viruses.Conclusions: The study indicated that the quality of death certificates is less than satisfactory for the 1998 Australian mortality data. The findings may be helpful in clarifying the ICD coding rules and the development of disease prevention strategies.