Iron deficiency anaemia is one of most prevalent nutritional disorders worldwide. It is known to affect the health and cognitive ability of children and adolescents. Studies in Saudi Arabia concentrate only on the population of young children and pregnant females or girls. Studies on the whole school student population is lacking. The objectives of this study were to identify the nutritional habits and the prevalence of anaemia among school students in Jeddah, as well as to recognize the students' awareness of their anaemic nutritional status. Data were collected from a sample of Saudi school children in Jeddah City from 42 boys' and 42 girls' schools during the month of April 2000. Data collection was done by an in-person interview to collect socio-demographic factors, nutritional habits, weight and height. Haemoglobin was measured in a sample of 800 students selected at random from both genders and different age groups. Anaemia was defined according to the new WHO cut-off levels for haemoglobin as: blood haemoglobin <11.5 g/dl for the 5-11 years boys and girls; <12.0 g/dl for 12-14 years boys and girls; <12.0 g/dl for 15+ girls and <13.0 g/dl for 15+ years boys. Proportion and 95% confidence intervals (CI) were calculated and significance was considered when the 95% CI did not overlap. Anaemia was reported among 20.5% of school students. Anaemia was more prevalent among students of at least 12 years as compared to the younger age group. Also, anaemia was more marked among governmental school attendees and those born to low-educated mothers. Menstruating girls were at around double the risk of being anaemic than non-menstruating girls. Anaemia was associated with negative impact on school performance and was more marked among those who failed their exams as compared to students with excellent results. Skipping breakfast was reported by 14.9% of students and this habit did not differ by age, sex, body mass index or social class. Skipping breakfast was more marked among students with poor school performance as compared to those with very good or excellent results. Only 34.1% of anaemic school students were aware of being anaemic. Awareness was nearly equal in all age groups and social classes but girls were more aware of their anaemic status than boys. Iron deficiency anaemia appears to be prevalent among school students. At age 12 years and over, low social class and menstruating girls constitute the high-risk groups. Screening is recommended for high-risk groups and school health programs are crucial to improve students' nutritional habits, knowledge and awareness.