We have studied 29 school phobic youngsters (14 boys and 15 girls), of mean age 12 years 10 months (S.D. = 14.7 months) shortly before admission to an adolescent psychiatric in-patient unit. The diagnosis was made when there was severe difficulty in attending school, severe emotional upset at the prospect of having to go to school, staying home during school hours with the parents' knowledge and absence of significant anti-social disorders. Information was gathered from the patient and one parent, usually mother. Most youngsters had completely refused to go to school (23) and the remainder went occasionally with great reluctance; this seemed to depend on the attitudes of parents, school and medical agencies. Psychoses, gross physical illness, truancy, and neurotic disturbances other than school phobia resulting in absence from school were excluded. The cases were classified, reliably, into 19 ‘acute’ (11 boys, 8 girk) and 10 ‘chronic’ (3 boys, 7 girls) school phobics. This was done on the criterion of previous severe reluctance to attend school: at least 3 years of trouble-free attendance led to a classification as ‘acute’, the remainder were ‘chronic’. The mean age of the acutes (13 years 1 month) was significantly higher (P<0.001) than that of the chronics (12 years 3 months). In the acutes, the school phobia had been present 5 months (S.D. =3.5 months) on average in the boys, and 1 year 5 months (S.D. = 16.5 months) on average in the girls; which was a significant difference (P<0.02). The mean time between onset of symptoms and complete refusal was 3.5 months [boys-2 months (S.D. = 2 months) girls-6 months (S.D. = 9 months)]. The following features did not show significant differences between the acutes and chronics; social class of the patient's father (the typical social class was 5a on the Hall and Jones Scale of Occupational Prestige for Males), the mean age of mother when the child was bom, the number of only or youngest children in the family, birth complications, the number of severe illnesses, accidents and operations added to separations from mother in the first decade, missing some school without the parents' knowledge, suicidal gestures, the occurrence of symptoms on transfer to secondary school, somatic symptoms, frank mental illness in parents and I.Q. (W.I.S.C. total score); 4 acute cases had symptoms coming on following a bereavement.