This study investigated the effect of attending pre-school on mucosal immunity. Children 3.5 to 5 years of age who attended pre-school were observed for a 10 month period. Demographic information was collected on previous childcare experiences, the home environment and clinical information relating to the child and the family. A daily illness log was kept for each child. A multivariate longitudinal analysis of the relation between immunoglobulins in saliva and age, gender, childcare experience, pre-school exposure, number of siblings, environmental tobacco smoke (ETS), atopy and hospitalisation was conducted. There was a positive association of higher IgA levels with the winter season and with children being older than 4 years (P <.001), having attended childcare prior to commencing pre-school (P <.05), and having been exposed to ETS at home (P <.05). Lower IgA levels were associated with being atopic (P <.05). Higher IgG levels were associated with exposure to ETS (P <.001), while lower levels were associated to having atopy. Higher IgM levels were associated with previous childcare experience (P <.01) whilst having been hospitalised was associated with having low salivary IgM levels (P <.01). Lagged analyses demonstrated that immunological parameters were affected by the number of respiratory infections in the preceding 2 months. © 2010 Patricia Ewing et al.