Pulmonary exacerbations (PEx) in Cystic Fibrosis (CF) are associated with an increased morbidity and even mortality. We investigated whether early detection of PEx in children with CF is possible by electronic home monitoring of symptoms and lung function. During this one-year prospective multicentre study, 49 children with CF were asked to use a home monitor three times a week. Measurements consisted of a respiratory symptom questionnaire and assessment of Forced Expiratory Volume in one second (FEV1). Linear mixed-effects and multiple logistic regression analyses were used. In the 2 weeks before a PEx, the Respiratory Symptom Score (RSS) of the home monitor increased (p = 0.051). The FEV1 as percentage of predicted (FEV1%pred) did not deteriorate in the 4 weeks before a PEx. Nevertheless, the FEV1%pred at the start of exacerbation was significantly lower than the FEV1%pred in the non-exacerbation group (mean difference 16.3%, p = 0.012). The combination of FEV1%pred and RSS had a sensitivity to predict an exacerbation of 92.9% (CI 75.0-98.8%) and a specificity of 88.9% (CI 50.7-99.4%). The combination of home monitor FEV1%pred and RSS can be helpful to predict a PEx in children with CF at an early stage.Pulmonary exacerbations in Cystic Fibrosis (CF) are important events, associated with an accelerated decline in lung function and an increased morbidity and even mortality 1 . Prevention of pulmonary exacerbations (PEx) is one of the main goals in the management of CF 2 . Currently, treatment of a PEx starts when a patient presents with an increase in (respiratory) complaints, a deterioration in lung function and/or weight loss. It often takes some time before a patient with more complaints seeks medical care. This patient delay may introduce a subsequent delay in starting antibiotic treatment, potentially resulting in a more severe course of the PEx, and a higher risk of permanent lung function loss.There are some known risk factors for PEx in children, including frequency of previous PEx, a lower baseline Forced Expiratory Volume in one second (FEV 1 ), and female sex 3 . However, in individual cases these factors do not help to decide when to start therapy timely. As PEx cannot be predicted reliably yet, there is a need for a method to detect PEx at an earlier stage. Electronic home monitoring may be useful to detect changes in lung function and respiratory complaints at an early stage. It provides the opportunity to assess symptoms and lung function on a daily or weekly basis. Data can be sent to the CF centre where they can be evaluated. In this way, disease deterioration and the occurrence of PEx may be detected earlier.