The Maternal Behavior Q-Sort (MBQS) assesses the maternal sensitivity of mothers of 0-3 year-olds in natural contexts. This study presents the results of MBQS 3.1 convergent validity with version 2.1 and criterion validity with the Attachment Q-Sort (AQS). The sample was comprised of 27 Peruvian mothers with children between 8 and 11 months old, from a low socioeconomic sector in Lima. The mean age of the mothers was 27.96 years (SD=6.02) and most reported at least some high school education (63%). The maternal behavior profiles in MBQS 3.1 - sensitive, connected, and synchronic - correlated with values higher than.90 (p<.01). A strong positive association was found between versions 2.1 and 3.1 (r=.76, p<.01). Finally, a correlation of.44 (p<.05) was obtained with AQS. The MBQS 3.1 shows adequate validity indicators, which recommend its use for the measurement of maternal sensibility in Peru.