This case control study was conducted to determine the frequency of nutritional rickets among hospitalized infants and to assess their relation to respiratory diseases. All infants between the age of 3 months and 2 years admitted to the pediatric ward of Queen Alia Military Hospital during the period February-October 2001 were examined and investigated to rule out nutritional rickets. Children admitted for the first time to hospital for acute illnesses were only included in the study. A special data collection sheet was designed for this study which includes information on the age, sex, causes of admission, family size, the rank of the child in the family, family monthly income, outdoor clothing habit of the mother, and the mode of feeding. Data were collected from the infant charts and/or by interviewing the child's mother or guardian. Clinical signs of rickets were also recorded, including rosary beads, craniotabes, wide anterior fontanel, delayed dentition, widening of epiphysis, bowing of the legs, and double malulous. Blood sample was collected for calcium, phosphorus, alkaline phosphatase, and hemoglobin level. Those infants with any clinical sign of rickets and/or abnormal chemical results had a wrist X-ray to confirm the diagnosis of rickets. The rachitic group (cases) was compared for statistical significance with the remaining non-rachitic infants (controls) for the data collected. Rachitic infants received intramuscular 600,000 IU of vitamin D; a follow-up wrist X-ray and blood sample for calcium, phosphorus and alkaline phosphatase was arranged 3 weeks later. Forty-seven infants (10.6 per cent) out of the 443 included in the study were found to have nutritional rickets. Forty (85.1 per cent) of the rachitic infants were admitted due to lower respiratory tract diseases compared with 30 per cent of the control group and the difference was statistically significant (p < 0.01). Duration of hospital stay in the rachitic infants was also significantly more prolonged than the non-rachitic control group (9.5 days vs. 7.4 days, p = 0.002). Rachitic infants were breastfed in 82.9 per cent, ranked second or more in the family in 87.2 per cent, and had mothers who wore head cover outdoors in 80.8 per cent compared with 60.8, 40.1, and 60.3 per cent, respectively, in the non-rachitic group (p < 0.01). High alkaline phosphatase, hypocalcemia, hypophosphatemia, and anemia was found in 100, 19, 50, and 78.7 per cent, respectively, in the rachitic group compared with 9.8, 2, 1.2, and 43.7 per cent, respectively, in the control group (p < 0.001). Nutritional rickets seems to be a common problem among infants in Jordan. Further studies at national level are needed to determine the prevalence of rickets in Jordan. Rachitic infants are commonly hospitalized due to lower respiratory tract infections, thus there is a high index of suspicion for rickets among hospitalized infants with lower respiratory tract diseases.