Immunoglobulin isotypes (IgG, IgA, IgM, IgD, IgE) in serum were investigated in 64 Libyan children with mild to moderately severe asthma (age: 1-12 years; sex: 39 males, 25 females) (Group A) and in 57 healthy Libyan children (age: 1-12 years; sex: 30 males, 27 females (Group B). The patients were classified according to age into three groups (A1: 1-3 years; A2: > 3-5 years; A3: > 5-12 years); according to disease activity into two groups (AA: active disease; NA: inactive disease); and according to age plus disease activity into six groups (AA1, NA1; AA2, NA2; AA3, NA3). The healthy children were also divided according to age into three groups (B1: 1-3 years; B2: > 3-5 years; B3: > 5-12 years). IgG, IgA, IgM and IgD were measured by radial immunodiffusion method and IgE was estimated by enzyme immunoassay technique utilizing immunokits from bioMerieux, France. Serum levels of IgG, IgD and IgE were elevated significantly in patients compared to controls (A vs B: p 0.05). IgG and IgD levels were raised in A3 (p < 0.05), while IgD levels were raised in both A2 and A3 (p < 0.05) and IgE was elevated in all age groups (p < 0.05). However, IgG was elevated significantly in AA only, while IgD and IgE levels were high in both AA and NA (p < 0.05) and IgE was even considerably higher in AA compared to NA (p < 0.02). Further elevated levels were observed for IgG in AA3 only (p < 0.05), for IgD in NA2 (p < 0.01), AA3 (p < 0.01) and NA3 (p < 0.05) and IgE was much higher in patients with active disease than with inactive disease in all age groups (p < 0.05). The fact that asthmatic attack in majority of our patients can be explained as mediated through IgE and the possibilities that IgG and IgD may play roles as aetiopathogenetic or protective regulatory factors in childhood asthma are discussed.