OBJECTIVE The paper, conceived as a retrospective study, resumes the results of our own investigations of the presence of serum IgG antibodies against Toxocara canis (as a crossover also against T. cati) in the sera of patients suspected of presenting larval toxocariasis in the region of Eastern Bohemia of the Czech Republic in the years 1997-2002. Our aim was to determine the immunity rate of IgG, its relationship to age and sex, further the whole range of diagnoses, the frequency of demands for such an examination by physicians and the evaluation of our experience with the detection of low avidity IgG. METHODS With a commercial diagnostic kit the ELISA method was used to detect the presence of IgG antibodies against T. canis in 2 994 sera. IgG avidity was determined in 92 positive samples with an avidity solution, which is included in the diagnostic kit and has been used in our laboratory since 2001. RESULTS The immunity rate of larval toxocariasis in our set was 20.4 % (612 samples). With age this rate increases (in individual decades of life - 11.9; 8.3; 11.4; 17.9; 26.1; 29.8 and 34.2%). Up to adolescence positive findings predominate among boys (males 0-10 years 84.2 %; 11-20 years 76 %). In the third decade we see a dramatic change in favour of women (women 21-30 years - 74.6 %). In absolute figures the number of positive findings stagnates in men after the age of 30 years, while among women positive findings continue to grow - yet expressed in percentages there is signifinct change in the male-female ratio (beginning with the 4th decade we find among the women 61.2; 69.7; 72.6 and 64.8 %). Physicians' interest in the diagnosis of toxocariasis in the years 1997-2002 is confirmed by the significantly higher number of investigated samples (135; 446; 617; 422; 558; 816). This, however, does not go hand in hand with a higher proportion of IgG positivity. IgG avidity was investigated in 92 positive samples - low avidity was confirmed in six of them (6.5 %); the appropriate case histories are not a part of the study. CONCLUSIONS Our results tally with the data published by other departments in the Czech Republic. They confirm that the methods used have, as before, their place in the diagnostic range of microbiological laboratories.