Efficacy and safety of mepiphylline, a derivative of theophylline, was evaluated in a group of children, aged 6 to 10 years, with mild or moderate acute asthma. A parallel, randomized, double-blind, placebo controlled, prospective study was performed in 40 children. Twenty one of them received mepiphylline in dose of 8 mg/kg/día divided in 3 during 10 days, and 19 (control group) received placebo. Salbutamol aerosols were available in both groups. Clinical and spirometric data were collected before the beginning of the treatment (pre-and-post-nebulized salbutamol), and at the 3rd, 7th and 10th days. Children and parents cooperated with a diary of symptoms, peak-flow measurements and account of salbutamol used. A total relief of symptoms was found in 14 patients in the mepiphylline group and just 8 of the control group, with no significant differences. Neither spirometry nor diary data showed significant differences. Salbutamol was less than 3 days of unnecessary in 13 patients (61.9%) in the mepiphylline group and 8 patients (42.1%) in the control group (p < 0.05; Kolmogorov-Smirnov two samples Test). We conclude that mepiphylline could be a complementary treatment of mild and moderate acute asthma with a good safety in children.