Abstract: The present invention provides a photodosimeter for use by sunbathers and the like and which activates an alarm when a predetermined radiation dosage has been received by the user. The photodosimeter includes a photocell exposed to the sunlight and which provides an analog output signal to an analog to digital (A/D) converter proportional to the radiation which impinges upon the photocell. The A/D converter provides an output signal to a microprocessor which periodically samples the output from the A/D converter and maintains a count in memory proportional to the radiation exposure. This count is divided by the solar protection factor (SPF) of any sunscreen material which is applied to the user's skin and the SPF factor is inputted to the microprocessor via a keyboard. When the count in the counter exceeds a predetermined maximum, an alarm is activated warning the user that the maximum radiation exposure of the user has been reached.