A school health programme in Mwera Division, Pangani District included treatment of malaria attacks occurring in children during school time. A combination of symptoms (headache, muscle/joint pains, feeling feverish) and oral temperature > or = 37.5 degrees C was used for the diagnosis of malaria. Chloroquine (25 mg/kg given over 3 days) was used for treatment. Malariometric surveys on children aged 7-15 years (mean 10 years) were conducted once a year (1995-1997). Plasmodium falciparum accounted for 100% of infections and the parasite prevalence varied between 32.7 and 35.3% from 1995 to 1997. The number of malaria cases (cases/1000 registered school children) diagnosed and treated by school teachers was 159 (67) in 1995, 324 (124) in 1996, 348 (128) in 1997 and 339 (108) in 1998. Children in grades 1-4 (age 7-13) accounted for 64.6% of cases. Symptoms and oral temperature were recorded for 1258 children. Of those, 992 (78.9%) complained of fever and at least one other symptom when presenting to teachers, 98 (7.8%) had fever as their only complaint and 168 (13.5%) presented without a perception of fever, but with other symptoms. Of these children, 36 (21.4%) had a temperature > or =37.5 degrees C. The sensitivity of "feeling feverish" was 96.5% with a specificity of 54.5%. The positive predictive value of feeling feverish was 89.9% and the negative predictive value 78.6%. Blood slides were prepared from 55.3 and 37.2% of children diagnosed by teachers during 1995 and 1996, respectively, and 71.4% were found positive. Among children who fulfilled the algorithm criteria 75.0% had a positive blood slide. With little training and regular supervision it was feasible for school teachers to make a presumptive diagnosis of malaria. We conclude that teachers can play a major role in school health programmes and are willing to be involved in health matters as long as they are supported by health and educational authorities.