Attachment and survival of Boophilus decoloratus and B. geigyi larvae were examined using skin slices from cattle, sheep and goats. Results indicate that B. decoloratus has a wider range of temperature (24-40 degrees C) at which more than 50% of larvae would attach to bovine skin, while B. geigyi has a narrower range (24-30 degrees C). The larvae of both species had two peaks of attachment--the 4th and 20th hour, the value for the second peak being greater than the first. The influence of humidity on larval attachment was only apparent where the temperature was high, and in such cases more than 70% of B. decoloratus larvae attached, while less than 20% of B. geigyi larvae attached by the 20th hour. Less than 50% of larval attachment was recorded on both sheep and goats. The results are related to the geographical distribution of both species in Nigeria, and to the problems of tick water balance, stimuli for tick attachment and host specificity.