We report on the methodology and first results from the Deep Lens Survey ( DLS ) transient search .
We utilize image subtraction on survey data to yield all sources of optical variability down to 24 ^ { th } 
magnitude .
Images are analyzed immediately after acquisition , at the telescope and in near–real time , to allow for followup in the case of time–critical events .
All classes of transients are posted to the web upon detection .
Our observing strategy allows sensitivity to variability over several decades in timescale .
The DLS is the first survey to classify and report all types of photometric and astrometric variability detected , including solar system objects , variable stars , supernovae , and short timescale phenomena .
Three unusual optical transient events were detected , flaring on thousand–second timescales .
All three events were seen in the B 
passband , suggesting blue color indices for the phenomena .
One event ( OT 20020115 ) is determined to be from a flaring Galactic dwarf star of spectral type dM4 .
From the remaining two events , we find an overall rate of \eta = 1.4 ~ { } { events } ~ { } { deg } ^ { -2 } ~ { } { day } ^ { -1 } on thousand–second timescales , with a 95 \% confidence limit of \eta < 4.3 .
One of these events ( OT 20010326 ) originated from a compact precursor in the field of galaxy cluster Abell 1836 , and its nature is uncertain .
For the second ( OT 20030305 ) we find strong evidence for an extended extragalactic host .
A dearth of such events in the R passband yields an upper 95 \% confidence limit on short timescale astronomical variability between 19.5 < \mathcal { M } _ { R } < 23.4 of \eta _ { R } < 5.2 ~ { } { events } ~ { } { deg } ^ { -2 } ~ { } { day } ^ { -1 } .
We report also on our ensemble of astrometrically variable objects , as well as an example of photometric variability with an undetected precursor .