The chemical composition of nine samples of Labofeed H (LH) breeding diet produced by Feeds and Concentrates Production Plant of A. Morawski (Poland) in 1997-1999 was in agreement with declared values except for a slightly lower fat content. The content of nutrients, minerals and essential amino acids conformed with the requirements of laboratory rats and mice for growth and reproduction, given by NRC (1995), except for a lower sulphur amino acids content. Composition, determined nutritional value of protein and metabolisable energy concentration, as well as the effects of feeding LH on growth performance did not differ from the values of the breeding diet produced by Altromin. The diet Labofeed B, designed for adult animals, had lower protein and metabolisable energy concentrations than LH and a similar nutrient profile as the respective Altromin maintenance diet.