Purpose: It is important to advise parents when to consult a doctor when their child has fever. To provide evidence-based, safety-net advice for young febrile children, we studied the risk of complications, the occurrence of alarm symptoms, the duration of fever. Methods: In a 7-day prospective follow-up study, we included 463 consecutive children aged 3 months to 6 years who presented with fever at a general practitioner out-of-hours service. We excluded 43 children with complicated illnesses at presentation. In a structured assessment, the duration of fever before presentation was noted and a physical examination was performed. Parents reported alarming symptoms and rectal temperature in a diary for 1 week. The total duration of fever included its dura Results: During follow-up, 3.2% of the children with uncomplicated illness at presentation developed a complicated illness. The presence of alarming symptoms dropped from 79.3% at day 2 of the fever episode to 36.7% at day 9. The estimated median duration of the total fever episode was 4.0 days (95% confidence interval, 3.6-4.4). Conclusions: In children with uncomplicated illnesses, the daily occurrence of alarming symptoms reported by parents was high. The median duration of fever was 4 days. The predictive value of alarming symptoms reported by parents for complicated illness should be reconsidered.