The present study investigated whether maternal aggression has shown a correlated response in a program of artificial selection for isolation-induced interfemale aggression in housemice. Females from the first replicate of lines (H1, C1, L1) and the second replicate of lines (H2, C2, L2) from generation S5 were given daily aggression tests for 20 consecutive days following the birth of their first litter. Evidence of a correlated response was found for replicate 2, but results for replicate 1 provided no evidence of a correlated response. In generation S10, when better separation of the lines on isolation-induced aggression had occurred, the study was repeated. In S10 there was clear evidence of a correlated response in both of the replicates.