  The F-statistic is an optimal detection statistic for continuous
gravitational waves, i.e., long-duration (quasi-)monochromatic signals with
slowly-varying intrinsic frequency. This method was originally developed in the
context of ground-based detectors, but it is equally applicable to LISA where
many signals fall into this class of signals. We report on the application of a
LIGO/GEO F-statistic code to LISA data-analysis using the long-wavelength limit
(LWL), and we present results of our search for white-dwarf binary signals in
the first Mock LISA Data Challenge. Somewhat surprisingly, the LWL is found to
be sufficient -- even at high frequencies -- for detection of signals and their
accurate localization on the sky and in frequency, while a more accurate
modelling of the TDI response only seems necessary to correctly estimate the
four amplitude parameters.
